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Linda Echegaray
Climate Change Paper
Regulation of Greenhouse Gases in Commercial Aviation
I. Introduction
When the Wright Brothers began testing what would be come to known as the airplane in
1900, they could not have imagined how their invention changed the face of travel and
innovation. The first airplane was essentially a giant kite with rudimentary controls to steer it
around. Sixty-nine years later, the United States, building on the technology, put a man on the
moon. Today, military aircraft travel at twice the speed of sound on a regular basis, shuttles have
been sent to Mars with specialized robots, commercial aircraft shuttle 300 people from Los
Angeles to New York, a distance of nearly 3,000 miles, in five and a half hours, and packages
can be shipped overnight from Juneau, Alaska to Miami, Florida. Not even George Orwell
imagined this level when he wrote “1984” in 1949.
However, with innovation and the expansion of scientific knowledge, the planet has now
learned that in our fascination for flight over the last 110 years, we have added to what is now
known as the global warming problem. Commercial jets use kerosene in the engines, which
yields carbon dioxide (“CO2”) , water vapor, Nitrogen (“N2”), Oxygen (“O2”), nitrogen oxides
(“NOx”) , Unused hydrocarbons (“UHC”), carbon monoxide (“CO”), soot (CPM), and sulfur
oxides (“SOx”) when burned. Out of these products, four are criteria pollutants under the Clean
Air Act (“CAA”) and one is considered a chief culprit in global warming and another is
considered another factor in anthroprogenic (human-induced) global warming. For this reason,
several environmental groups have sought regulation of the aviation industry and law review
articles have been propagated suggesting ways that it can be regulated. The problem lies in that

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very few of these articles actually address the physics of flight. Consequently, their conclusions
are not always feasible to the industry.
Emissions reduction is a trade off. Should designers forgo a quiet engine to decrease
carbon emissions? Should noise be reduced at the expense of increased carbon emissions?
Speed and altitude reduced to prevent condensation trail formation? To completely analyze this
problem, this paper is first going to address the basics of aviation, the various environmental
laws effecting its regulation, the proposed solutions to the climate change problem, and the
viability of the solutions. Overall, it appears a more laissez-faire approach may be what helps
the commercial aviation take off to reduce emissions.
II. The Basics of Flight
In order to truly understand whether certain measures for GHG regulation in commercial
aviation are viable, it is critical to understand some basics with regard to flight. Altitude,
humidity, wind direction and speed, the weight and balance of the aircraft, the age of the aircraft,
the size of the airport, the maneuver the aircraft is completing, and the purpose for the travel are
all going to have impacts on the amount of emissions that an aircraft releases. For this reason, I
am going to begin with four areas that address the legal and regulatory aspects: airspace, weight
and balance and its effect on fuel efficiency, taxiing, take-off and landing, and some differences
between different aircraft usage.
A. Airspace limitations of commercial v. private aircraft
Airspace is a three-dimensional object. While many people see this, they do not
generally realize the consequences of this with regard to flight. When you drive an automobile,
you worry about what is in front of you and where you are going. Aircraft do not have lanes to

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operate in and therefore must constantly be aware of what is all around them: above, below,
right, left, front, and back. Air traffic controllers help alert pilots when other aircraft are nearby,
but they cannot fly the plane for the pilot and their information is only as good as the function of
the radar that has been in use since the 1960s. Furthermore, larger aircraft produce what is
known as “wake turbulence” from their jet engines. If they come too close to a small, single-
engine airplane, they could easily throw them off-course or even produce a spinning stall (think
“jet wash” in Top Gun). For this reason, the Federal Aviation Administration (“FAA”) has
designated airspace restrictions based largely on the type of aircraft that you are operating.
Private aircraft, commercial aircraft, and military aircraft all have their separate spaces to operate
in. Depending on airport size and the presence of a tower, airports will list their airspace as
Class G, Class E, Class D, Class C, or Class B with Class B being the largest airports and the
most restrictive. Class A airspace is reserved for aircraft operating at high cruise altitudes.
Restricted airspace, or Special Use, is for military use.
Private aircraft operate at the lowest altitudes and generally out of Class G, E, D, or C
airports. When a private aircraft is not in a particular airport’s immediate airspace, they
generally have a ceiling of 9,000 feet above sea level (“ASL”) when at cruise altitude. Regional
(short distance and business jets) commercial aircraft tend to cruise in the airspace between
15,000-20,000’ ASL, and commercial jets cruise between 25,000 and 40,000 ASL. Each time
the pilot wants to enter the area for a new airport or different airspace, they must ask permission
from the air traffic controller (“ATC”). Class B airspace is predominantly for commercial
aircraft that are taking off or landing. Unauthorized penetration of Class B airspace, or worse
yet, restricted airspace, by non-commercial or non-military aircraft is a serious offense that could
mean the suspension of a pilot’s license.

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Commercial passenger aircraft operate above 15,000 feet unless they are landing or
taking off. Once the commercial craft leaves Class B airspace, they enter Class A airspace.
Class A covers all flights between 18,000 and 60,000 feet ASL. The length of the flight is going
to determine the altitude and size of the craft. As the altitude increases, the air becomes thinner.
For the purposes of engine function, only the more powerful jet aircraft can operate in altitudes
above 25,000 feet ASL (normally 30,000’ to 40,000’). Turboprop aircraft, usually used as
regional aircraft, are limited to 25,000 feet. Additionally, the more powerful jet engines are
attached to the larger aircraft that can carry more than 200 passengers. Commercial aircraft are
required to stay on a particular flight plan and keep in contact with the local ATC as they enter
their airspaces. If they wish to alter altitude due to turbulence, they must first call the ATC to get
clearance.
Special use airspace (“SUA”) is generally for military testing. For reasons of safety and
national security, no other aircraft are permitted in these restricted areas at certain times. Special
use has designated times that vary daily. For instance, on March 28, 2010, restricted airspace
near Edwards Air Force Base had SUA in operation from zero to 6,000 feet above ground level
(“AGL”), about 8,800 feet ASL, in effect until March 29, 2010. That means during those times,
no aircraft are permitted to operate within those altitudes. Some restricted airspaces, like the one
off the coast of Southern California or another in Nevada near the California border, do not allow
any aircraft and their SUA encompasses the entire month for all craft between zero and 99,000
feet AGL.
B. Weight & balance and its effect on fuel efficiency
Fuel efficiency in an aircraft is predominantly determined by the weight of the cargo.
Every aircraft has a designated center of gravity (“CG”). Like a see-saw, if too much weight is

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towards the front, the plane tips forward, and in some cases, will not take off. The more weight
pressing down, the more thrust is required to get the airplane off the runway. For this reason, all
aircraft include the maximum take-off weight in their operator’s manuals. There are two things
that are the most memorable in any pilot’s first solo flight in an airplane: (1) the ease in which
the plane seems to pop off the ground, and (2) the total silence in the cockpit created by the
instructor’s absence.
Gas mileage in an airplane is not measured in miles per gallon, but minutes per gallon or
seat miles per gallon. For example, a Cessna 172, which is a private four-seater airplane, gets
about eight minutes of travel time per gallon. Commercial jets get between 0.015 and 0.02
gallons per available seat mile (“ASM”). To put this in more familiar terms, if a commercial jet
seats 300 passengers, it uses an average of 4.5 – 6 gallons in a mile.1
Additionally, a one-percent
reduction in the gross weight of an empty aircraft will reduce fuel consumption between 0.25%
and 0.75%.2
In calculating the take-off weight, the variables that an operator needs to consider are (1)
the weight of the fuel, (2) the weight of the baggage, and (3) the weight of the passengers. An
airline’s second largest expense is fuel at 15%, so airlines have a great deal of motivation to
conserve fuel usage and save costs.3
With the drop in air travel due to the economy in the last
few years, airlines are achieving this goal by charging for baggage brought onto the aircraft and
are only putting the amount of fuel they will need for the trip. Again, the less weight added to
the airplane by passengers, fuel, and baggage, the more easily it pops off the ground. This goes
back to why the student is so surprised on their first solo take-off. When the instructor is in the
plane, an extra 200 lbs., on average, is added to the weight, so it takes longer for enough lift to

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accrue for the plane to take off. Removing that one person makes a huge difference in how the
aircraft leaves the runway.
C. Taxiing, takeoff and landing: physics and general rules
The first thing to understand with regard to taxiing is that the wheels on the aircraft are
not attached to any steering system. A plane moves right or left on the ground by moving its
rudder flaps. Therefore, an aircraft’s ability to steer on the ground can easily be impeded by
winds. The greater the adverse wind, the more fuel is necessary to taxi the aircraft. Part of
taxiing is taken up with what pilots call a run-up. This is when you hear the engine of the
aircraft increase in intensity for a minute and then go back down. This is not the pilot’s
impatience, but a necessary safety check. While an aircraft is on the ground, the engine is using
minimal power. However, take-off and cruise flight require a higher rotation per minute (“rpm”)
on the engine, so it is necessary to test the integrity of the flight systems at that rpm while still on
the ground. Once the run-up is complete, the pilot has to get permission from the ground
controller to take off. It is important to note commercial jets have multiple engines -- a Boeing
727 has four engines while a Boeing 777 only has two4
-- so many airlines only use one engine
while taxiing to conserve fuel.
Taking off requires 100% thrust and therefore also requires the greatest amount of fuel.5
In order to take off efficiently, the aircraft must go against the wind to create the necessary
friction, or lift, to get the aircraft off the ground. The pilot pushes the throttle all the way in, he
waits for the aircraft to build enough speed (each aircraft has a different speed where lift
generates depending on weight), and then pulls up the yoke (the aircraft’s steering wheel).
Pulling up the yoke makes fins on the tail go down and the nose point up. This increased surface
area of the plane being exposed to the wind increases the pressure below the aircraft. Once the

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pressure beneath the wings is greater than the pressure above the wings, the aircraft becomes
airborne. The throttle remains in, or most of the way in (85%), until the pilot reaches cruise
altitude. Once cruise altitude is reached, the pilot brings the rpm down to the manufacturer’s
recommended cruise rpm and adjusts the mixture of air and fuel going into the engine to increase
efficiency.
Landing requires significantly less fuel than taking off. When an aircraft is landing, it
must first reduce its speed. To accomplish this, the throttle is taken down to less than 30%, the
landing gear is released, and the flaps are deployed. The pilot keeps the aircraft nose up to allow
the adverse wind to accomplish the additional loss of airspeed that the flaps and gear did not
alleviate, and gently lands on the runway, rear landing gear first.
D. Separating commercial air travel from other air travel
For the purposes of this paper, it is critical to note that commercial air travel is going to
be the predominant mode addressed. Not many statistics are available on private aircraft,
defined as two to six-seater aircraft travelling below 10,000 feet, or business jets. Additionally,
military aircraft will not be addressed due to their regulatory exemptions. The information
available shows that freight air traffic in the United States has increased by a factor of 2.7
between 1981 and 2000 and accounts for much of the high-altitude air traffic.6
Unfortunately,
there have not been many studies addressing the impact of freight service on GHG emissions.
III. Commercial Aircraft’s Impact on Climate Change
Various environmental groups have sought more stringent regulation of the aviation
industry due to the Nitrogen Oxides, Sulfur Oxides, Carbon Dioxide, Soot (particulates), and ice
trails left by aircraft as they expend fuel to obtain the energy they need. Although aviation only

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accounts for roughly nine percent of transportation’s carbon footprint in the United States7
, 3.5%
of the problem internationally8
, it has been estimated that its impact is two to four times greater
than for CO2 alone and is expected to grow over the next twenty years.9
Additionally, studies
show that in 1999, Southern California paid $30,000 per ton for various NOx reduction
methods.10
There are three basic aspects to the climate change issue with regard to commercial
aviation: (1) condensation trails forming cirrus clouds and adding to the anthroprogenic warming
of the earth, (2) greenhouse gas (“GHG”) emissions at high altitude, and (3) the predicted
expansion of the industry in conjunction with its international entanglement. Each of these will
be addressed in turn.
A. Contrail Formation and Its Impact
One of the largest debates is over the formation of condensation trails, or “contrails,”
commercial aircraft emit at altitudes above 30,000 feet. Contrail formation studies have gone
back as far as 1919, but the first definitive work by Appleman on the conditions necessary for a
contrail to form and how they form was not published until 1953.11
Studies after 1953 have
focused on different variables effecting formation, how long it takes the contrail to form, and
what the contrail’s composition is for application in military aircraft. Stealth capability is
pointless if the enemy can see the contrail. In order for a contrail to form, the temperature must
be -45 degrees Celcius or less depending on the humidity.12
The lower the humidity and vapor
pressure of the air, the lower the temperature has to be.13
It is the same as frost build-up on your
car. If there is not a great deal of humidity in the air, it has to be really cold for frost to form.
NASA has developed equations for estimating air temperature based on altitudes. The
troposhere, defined as altitudes less than 36,152 feet (or 11 km) has the equation Temperature (in

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Farenheight) = 59 – (0.0036 x altitude in feet).14
Using this equation, an aircraft flying at 30,000
feet is experiencing an external temperature of roughly negative 49 degrees Farenheight, or
negative 45 degrees Celcius on avergae. The actual temperature will vary according to latitude,
time of day, and time of year. For heights above 36,152 but less than 82,345 feet, the layer of
atmosphere is called the lower stratosphere. The lower stratosphere has been measured at
negative 70 degrees Farenheight or negative 57 degrees Celcius and does not vary according to
altitude or season.15
What this means is that aircraft flying above 36,152 are almost always in
conditions favorable to contrail formation and aircraft flying between 30,000 and 36,152 feet are
dependent upon latitude, season, time of day, higher humidities and pressure to form contrails.
On average, 27,350 high-altitude (flights above 25,000’) commercial flights occur each week in
the United States according to data samplings from 2000-2003.16
If half of these flights reach
altitudes above 36,152 feet, that means there are roughly 13,675 flight per week that have the
ability to form contrails.
Contrails are composed predominantly of frozen water vapor measuring 2-6μm in
diameter, but can also contain some frozen Sulfur and Carbon-based emissions.17
The
environmental concern is when contrails are formed consistently in areas, they cause additional
cirrus cloud formation. The additional cirrus clouds add to the warming of the atmosphere since
they refract heat back to the earth’s surface causing what is known as radiative forcing.
International Panel on Climate Change’s 2000 report shows that radiative forcing with regard to
contrails from aircraft is approximately 0.03 W (Watts) per square meter of air (m-2
).18
The
amount of radiative forcing varies by the amount of air traffic over the particular region. For
instance, Northern France showed 0.71 Wm-2
and New York City registered 0.58 Wm-2
.19
Additional studies have shown that high cloud cover has increased over the last hundred years.

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From 1982-1991, North America experienced a 5.6% increase in cirrus cloud coverage for the
entire region and a 13.3% increase over high air traffic areas with the greatest annual increases
over the oceans.20
B. How much GHGs do commercial aircraft emit?
In addition to contrails, aircraft emit unused hydrocarbons (UHC), carbon dioxide (CO2),
carbon monoxide (CO), soot (CPM), and nitrogen oxides (NOx). The carbon-based emissions are
all GHG concerns and the NOx emissions have a tendency to generate or destruct ozone thus
making them of concern to climate change as well.21
Typically, 60% of the NOx, 2% of CO, and
5% of HC occur at take-off while 5% of NOx, 65% CO, and 45% HC emissions occur on
approach.22
During cruise, 6% of the total mass flow emerging from the engine is CO2 while
only 0.3% is NOx and 0.04% is CO.23
In other words, the more carbon that an aircraft is
emitting, the less NOx emissions you can expect. This also shows that NOx emissions increase
with the increase in throttle power. As noted earlier, 100% throttle is used on take-off whereas
30% is used on approach. The amount of throttle used during cruise is completely dependent on
wind. Travelling east takes less time and fuel since winds generally come from the west due to
the Earth’s rotation.
Carbon dioxide emissions are anticipated to increase over the next forty years due to the
trend in jet fuel consumption. As of 1995, roughly one percent of the CO2 emissions came from
commercial aviation, but this figure could rise to above fifteen percent of emissions by 2050.24
Soot is another concern since it can trigger cloud formation and trap additional heat.25
A 1991
study of the South Coast Air Quality Management District showed that in the Southern
California region alone, 8000 tons of NOx were emitted and 20,000 tons of CO in that year.26
New York’s 1995 study by the EPA showed 23,000 tons per year for NOx and 31,000 tons per

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year for CO while Memphis’s 1990 study showed 4300 tons per year for CO, HC, and NOx
combined.27
Aircraft are designed to last thirty to fifty years and cost anywhere from $51.5 million to
$308 million each.28
They are not designed to be replaced like automobiles are. If an airline
needs to purchase 100 new aircraft for its fleet, it is looking at a minimum of $5 billion. Most
major air carriers have between 650 and 800 airplanes in their fleet in order to meet the demand.
Air carriers cannot afford to replace their fleets, especially when the aircraft are in working
order, so many studies anticipate carbon emissions to rise over the next twenty years regardless
of innovation.
C. Projection with regard to the growth of air travel
From 1960 to 1990, the demand for air travel grew at a rate of 9% a year while the 1990-
2000 demand grew 4.5% annually.29
It has been anticipated that the demand will continue to
increase 5% annually through 2015.30
In particular, regional air traffic appears to be growing the
fastest at a rate of 19.7% in 1999 and use a disproportionate amount of jet fuel based on the
percent of passenger revenue miles they encompass.31
The United States accounts for 24-26% of
the world market32
, but China’s aviation growth was 24% in 2005 while the UK’s aviation
industry grew 8%33
, making the increased demand of the aviation industry a growing problem.
IV. Current Regulation of the Aviation Industry and Proposed Solutions for Emissions
There are several sources of regulation on the aviation industry depending on what is
being regulated. For instance, the International Civil Aviation Organization (“ICAO”) controls
international standards with regard to trade between airlines and goals for the industry at large
with regard to safety and emissions. The United States Code of Federal Regulations (“CFR”)

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covers domestic safety regulations. In addition to these sources, the United Nations Framework
Convention on Climate Change (“UNFCCC”) has identified several goals with regard to GHG
emissions from the aviation industry.
A. ICAO Regulations and UNFCCC
The ICAO was established by the Chicago Convention on International Civil Aviation in
1944. Its initial purpose was to coordinate international air travel and to establish standards and
procedures for international civil aviation.34
Today, it promotes civil aviation through its 190
members.35
Each time a new environmental treaty has been ratified, the ICAO has taken actions
to help the industry comply.
In 1993, shortly after the Montreal Protocol went into effect, the ICAO reduced its initial
NOx emissions limits for engine certification by twenty percent.36
The Kyoto Protocol, first
envisioned in 1992, came into existence in 1997. Article 2.2 of the Protocol provided: “The
Parties included in Annex 1 (of the UNFCCC) shall pursue limitation or reduction of emissions
of greenhouse gases not controlled by the Montreal Protocol from aviation…working through the
[ICAO]...”37
Two years later, the ICAO further reduced the NOx limits for engines certified after
2003 by an additional sixteen percent.38
In addition, the Committee on Aviation Environmental
Protection (“CAEP”) for ICAO formed five working groups to address concerns relating to
aircraft noise, emissions certifications and limits, and market-based approaches to reducing
aircraft emissions.39
The most recent meeting of the ICAO pertaining to GHG emissions took place
September 18, 2007.40
Out of this meeting came Resolution A36-22, which called for “the
ICAO Council to form a new Group on International Aviation and Climate Change. This Group
is to be tasked with developing and recommending to the Council an aggressive Programme of

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Action on International Aviation and Climate Change.”41
In December 2009, the ICAO released
a statement with regard to the progress of the group and the agreement of the members. The
agreement provides for: (1) a 2% increase in fuel efficiency, (2) keep working on the climate
change problem with regard to aviation, (3) develop standards for CO2 emissions, (4) study
alternative fuels, (5) alter air traffic management to reduce emissions, and (6) monitor and report
the progress.42
The next full assembly meeting to solidify these goals is scheduled for May 11-
14, 2010 in Montreal, Canada.
B. CFRs and other Sources of Regulation on the Aviation Industry
The United States CFR reflects the resolutions of the ICAO by codifying certain
provisions for domestic effect. The particular provisions relating to engine emission certification
are located at 14 C.F.R. § 21.21. This regulation provides the engine for transport aircraft
(commercial aircraft) must meet “the type design and the product meet the applicable noise, fuel
venting, and emissions requirements of the Federal Aviation Regulations…”43
Title 42 of the
United States Code specifically addresses aircraft emissions as “moving sources” and requires
the FAA Administrator to look for feasible ways to reduce emissions and propose emission
standards for various classes of aircraft engines.44
The specific engine emission limits in 14 CFR
§ 34.21 include various standards depending on when the engine was manufactured. For
instance, aircraft engines manufactured on or after 1974 are limited to a smoke number of 30 and
engines manufactured after 1984 are limited to HC emissions of 19.6g per kilonewton thrust.45
Additional constraints on the aviation industry include trade agreements, such as the 2007
Air Transport Agreement reached between the European Union and the United States and placed
into effect March 30, 2008. The agreement allows United States-registered aircraft to fly from
one European Union state to the next without first returning to the United States.46
The

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agreement establishes uniform user charges, allows subsidies as long as they do not interfere
with the ability of other airlines to compete, and allows countries to be more strict than others
with regard to safety concerns.47
While these terms of the agreement predominantly address the
removal of restrictive trade practices, it also specifies “[w]hen a Party is considering proposed
environmental measures, it should evaluate possible adverse effects on the exercise of rights
contained in this Agreement, and…take appropriate steps to mitigate…”48
From this provision,
it appears that the interest of the members to the agreement is that one country not set limits
greater than those set by the ICAO with regard to environmental issues unless they mitigate the
effects while still preserving maximum efficiency in the industry. FAA and EPA may have a
hand in codifying limitations in the United States, but it does not appear that they will set
environmental regulations that are more stringent than those set by the ICAO in the interests of
international trade.
C. Proposed Solutions to Limiting Aircraft Emissions
As noted in the ICAO Copenhagen statement, several different proposals for reducing
aircraft emissions have been forwarded for consideration. It is important to note that each
solution comes with its own set of new problems. These solutions include cap-and-trade
systems, misting of aircraft engines during take-off to reduce nitrogen-based emissions, flying at
lower altitudes to avoid contrail formation, using alternative fuels, improving maneuvering
standards to increase fuel efficiency.
1. Cap and Trade under the European Union’s 2008 Emissions Trading Scheme
The European Union has recently instituted a cap-and-trade system for aviation in order
for them to meet their goal of 60% reduction.49
In the EU’s cap-and-trade system, all flights
taking off or landing in EU countries will be included in the emissions trading scheme as

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opposed to only intra-EU flights.50
Article 14 of the Emissions Trading Directive (“ET
Directive”), which took effect in 2008, requires aircraft operators to “report their greenhouse gas
emissions in accordance with these guidelines, which are legally binding.”51
The 2008 Directive
cited goals of limiting the average global temperature increase to no more than 20
C from pre-
industrial levels and CO2 reduced 50% below 1990 levels by 2050.52
The ET Directive requires
reporting of carbon emissions and NOx, but does not require contrail emissions reduction or
reporting. However, it does request that members of the EU promote solutions to reducing
contrail formation.53
Exemptions are in place for those carriers operating less than 243 flights
per period for three consecutive four-month periods.54
It is too soon to tell whether the program
is actually resulting in lowered emissions, however recent predictions show a decrease in profit
margins for the larger airlines due to the trading scheme.55
2. Reducing NOx Through Engine Function
In 2004, NASA published a study that proposed water misting in aircraft engines during
take-off and climb in order to reduce NOx emissions.56
More than 95% of NOx emissions occur
during take-off and climb alone, so focusing on this stage serves two purposes: (1) it addresses
the period when NOx emissions are of the greatest concern, and (2) it minimizes the excess
weight on the airplane since water will certainly add to the take-off weight.57
The study used a
305 passenger Boeing aircraft, the 777, at 100% thrust and 100% load in order to test the
effectiveness of the system.58
The results showed a 46% drop in NOx emissions with a 48.2 lb.
drop in the actual emissions during take-off and climb with those settings and noted that
everyday savings would be more since airlines generally only operate at 70% load.59
This system, while promising, has its setbacks. For instance, as the NOx emissions fall,
the CO and HC emissions rise.60
The added mass of the water also increases the cost per take-

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off by $20 for the water, $42-51 for fuel, $100,000-$200,000 per airplane to install the new
system, and engine maintenance costs of $9,200 per aircraft.61
However, it is critical to note that
this system also reduces smoke, aircraft engine noise, and saves $1663-1951 per ton in NO x
emissions reduction cost, roughly half the cost of an emissions trading credit.62
The estimated
bottom line for the system is an increase of $40.92 per LTO cycle.63
Divided between 300
passengers, this equates to 13.6 cents per person.
3. Alternative Fuels
In 2006, NASA addressed the feasibility of various alternative fuels for commercial
aircraft. The study revealed massive trade-offs depending on the area of emissions the airline is
seeking to reduce.64
For instance, liquid hydrogen may result in the least amount of CO2
emissions, but it has greater NOx and water emissions than regular jet fuel (kerosene).65
With
such disparity in results, it is critical to understand the different fuel options and the challenges
they present. Since Bio-Jet Fuel, Hydrogen, and Liquid Methane are the most promising options
as far as carbon emission reduction is concerned, I will focus on those.
Bio-Jet Fuels are actually a blend of petroleum fuels and soybean, rapeseed, or sunflower
oils.66
The plants are put through a chemical process to produce soy methyl ether (“SME”).67
The difficulty with using SME is that it tends to freeze at normal operating cruise temperatures (-
20˚C) and its lack of stability over time.68
For this reason, SME is usually blended with
petroleum diesel and makes up no more than twenty percent of the composition.69
An additional
problem with biofuels, even assuming that they could be approved for use in aircraft, is that a
sufficient quantity of crops cannot be grown to meet the supply demands in most countries.70
Supplying the US commercial aviation fleet with biofuel, at only a 15% blend, would require 34
million acres, about the size of Florida, devoted only to soybean crop.71

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Hydrogen and methane have different obstacles. Because they must be used in their
liquid form (both are gases at room temperature), they require heavy cryogenic fuel tanks and a
complete overhaul of how the aircraft is designed.72
The fuel tanks must be kept in the body of
the aircraft instead of the wings, they will increase the operating empty weight of the aircraft by
13%, and the airplane will require 28% more energy to complete a 500 nautical mile journey.73
However, due to the decreased weight of hydrogen in particular, the aircraft will be about 5%
lighter at take-off and there will only be a 2% increase in energy needs for a 3,000 nautical mile
trip.74
4. Alteration of Commercial Aviation Routes and Altitudes
Congress recently allocated $34.5 million to the FAA in order to update the air traffic
control equipment from radar to GPS and refer to the program as NextGen.75
The article stated
“the system is expected to save airlines money by allowing planes in crowded air corridors to
take more direct routes and fly closer to each other without safety risks, reducing delays, saving
energy and cutting down on pollution, including greenhouse gas emissions.”76
As it is, airlines
operate out of hubs. Due to this hub system, all of the flights must originate from the same
destinations. As a result, most of us have experienced the frustration of our flights taking us
from Los Angeles, CA to Atlanta, GA, in order to get to Dallas, TX, for instance. It would be
much more efficient if the aircraft flew directly from Los Angeles to Dallas. The GPS system
may not change this, but it could save a little fuel in the long run.
Due to altitude’s effect on contrail formation, experts have recommended the possibility
of lowering the cruise altitude of commercial aircraft to reduce this effect.77
Arguments for
lowering the altitude include a 50% reduction in NOx emission impact since it is no longer in the
sensitive region of the troposhere, and a 75% reduction in water due to lack of contrail

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formation.78
However, as with all other solutions, there is a trade-off: CO2 emissions would
increase by 15% and NOx could increase up to 25% without modifications to the engine.79
Contrail cirrus coverage is expected to increase from 0.1% to 0.5% by 2050.80
It is important to
note that while NOx emissions are responsible for the formation of ozone, they are also
responsible for the degradation of CH4 (methane), another greenhouse gas.81
V. Viability of the Proposals
Every solution has a trade-off. The question is which solution(s) are likely to work given
the current market and the state of technology. Which reductions are most important to reducing
aviation’s impact on global warming? I believe that under the circumstances, a combination of
solutions will need to be employed in order for member states to meet their goals under Kyoto.
This section will take a critical look at all the solutions presented: cap and trade, engine
modification and alternative fuels, modification of flight path and altitude, and the possibility of
additional regulation on the aviation industry.
A. Cap and trade
The European Union has already enacted a cap-and-trade system that encompasses all
flights taking off and landing in its airspace. The arguments for having the system are the same
as that for the Clean Air Act: it allows newer companies with the cleaner equipment to sell the
emissions credits they do not need to the more established companies that cannot afford to
replace their fleet. It allows flexibility while generating revenue. As noted earlier, the EU’s ET
Directive is expected to have a greater impact on profit margins to larger carriers. The question
is how this interacts with the rest of the regulatory scheme.

19. 19
For example, the Air Transport Agreement between the EU and the US includes a clause
that states “When a Party is considering proposed environmental measures, it should evaluate
possible adverse effects on the exercise of rights contained in this Agreement, and…take
appropriate steps to mitigate…”82
In cap-and-trade system for aviation, possible adverse effects
could easily be felt by those carriers outside the EU that make more than 243 flights in three
consecutive four-month periods. The ET Directive does not make reporting a requirement for
EU carriers, but any carrier landing and taking off in the EU more than 243 times in four months.
This equates to one arrival and departure a day. It is likely that many carriers from outside the
EU are making more than one take-off and landing per day. American Airlines alone showed ten
flights to Paris from Los Angeles on a given day.83
It will be interesting to see what the ICAO
decides when it meets again in May 2010 since cap and trade is one of the solutions its working
group has been researching.
Another disadvantage of cap and trade for the aviation industry is that there is not enough
information to see whether it actually reduces emissions to the level needed. Under the CAA,
the United States was able to reduce SOx emissions, but those were from stationary sources.
Aircraft are probably the most mobile sources on the planet. They emit over the entire course of
their journey, so setting a cap limit over a particular area is a difficult task. While an airline
company can estimate based on fuel usage and known emission indexes for that amount of fuel,
there is still the issue that emissions released in the upper troposphere and stratosphere travel
extremely long distances since they are carried on the wind in frozen form.
B. Alternative Fuels and Engine Modifications
1. Alternative Fuel in Commercial Use

20. 20
Alternative fuels show some promise with regard to emissions reduction. Bio-Jet Fuel
appears to be the most reasonable solution since it can be used in the current fleet of commercial
aircraft. Continental Airlines just completed its first successful test of jet fuel blended with bio-
jet fuel (algae oil and jatropha) on January 7, 2009.84
The Air Transport Association expects bio
fuels to be readily available for use in commercial aircraft by 2013.85
The Commercial Aviation
Alternative Fuels Initiative, founded in 2006, has reported recent success with a 50/50 biofuel
blend in a Thunderbolt II military aircraft at Eglin Air Force Base, agreements between airlines
and the Department of Defense to promote alternative fuels, and many other developments that
could pave the way towards widespread use.86
There are still several problems in this area. The actual cost of using biofuels is not
known. The NASA study recommended no more than a 20% blend in part due to the instability
of biofuels. If they are stored too long, they become unusable when the percentage is greater
than 20%. Additionally, the amount of crop necessary to meet current demands is not available
in the United States: 34 million acres of soybean crop. While alternative fuels do have promise
for commercial aviation, there is still a great deal of research to be done in order for them to be a
viable solution in the industry due to the amount of the supply that will be required and the cost
of implementation and storage.
2. Engine Modifications and Alternative Fuel Combined
Engine modifications, such as water misting to reduce NOx emissions, are very much part
of the cost/benefit analysis. Of the airlines surveyed with regard to the cost of the system, only
two responded.87
Both responded that they had used water misting in their older 747 engines and
noted higher operating cost and one operator noted that the water pumps would freeze on
occasion.88
However, they did state they would be interested in the new design proposed by the

21. 21
NASA study since it appeared to alleviate previous difficulties and limit the cost to $40.92 per
LTO cycle.89
However, there is still the issue with increased carbon emissions.
A study combining the carbon reduction of synthetic/biofuel blends and engine misting
technology would be extremely useful. It has been noted that biofuel usage is quickly becoming
available for use in commercial aviation and would reduce carbon emissions. At the same time,
the water misting system severely reduces NOx emissions, but only during the LTO cycle. NOx
emissions would still be an issue if released at high altitudes. Issues remain with either
technology in that the amount of crop required to meet demand for biofuel is not available in the
United States and the water misting system increases carbon emissions. While both show
promise, neither can solve the climate change problem on their own.
C. Alteration of Altitude and Flight Path to Reduce GHG Effects
Some have called for the decrease in altitude to avoid the impact commercial jets have on
radiative forcing both with regard to contrail formation and NOx emissions in the upper
troposhpere and lower stratosphere. Additionally, the FAA’s NextGen system has been
promoted and funded by Congress in an attempt to not only modernize aircraft tracking, but
reduce emissions and fuel burn by routing aircraft closer together without compromising safety.
Will either of these innovations reduce the effect aviation has on climate change?
1. Alteration of altitude to decrease contrail formation
Commercial airspace easily encompasses altitudes above 10,000’ and below 45,000’ with
most regional jets operating between 15-20,000 feet and larger commercial jets operating
between 30-40,000 feet. This disparity in altitude arguably allows large commercial jets to
reduce altitude 5-10,000 feet without compromising safety. As long as 1,000-2,000 feet of
altitude separate commercial jets, wake turbulence is not an issue.90
If a jet reduces its altitude

22. 22
from 40,000 feet to 30,000 feet, it is likely that it will prevent the formation of a contrail and
release of harmful emissions in the most sensitive portion of the atmosphere.
While this all looks great on paper, researchers have already noted that due to engine
design, this could actually increase the emissions. If an aircraft’s engine is designed to cruise
above 35,000 feet, then reducing that altitude will reduce the engine’s efficiency. The Boeing
747 and 777 are designed for cruise altitudes of 35,000 feet and 37,000 feet respectively91
and
the MD-80 is designed for cruise altitudes of 33,000 feet92
. If these aircraft cruise below these
altitudes, there will be a decrease in fuel efficiency resulting in a 25% increase of NOx emissions
and a 15% increase in CO2 without engine modification.
The overall GHG effect may decrease if aircraft cruise at lower altitudes, but it is difficult
to state whether the benefit will outweigh the cost of increased emissions and decreased fuel
efficiency. Arguably, if the engine is not running as efficiently, the airlines will require more
fuel which will add to the overall take-off weight. The increased thrust required for take-off and
climb will increase NOx emissions during the LTO as well as during cruise. The cost of the
engine modification is therefore the critical issue. While engine modification will be less
expensive than replacing the entire aircraft, it is unclear what the extra cost would be to achieve
this goal.
2. Alteration of Flight Paths to Maximize Efficiency
The NextGen system under construction in the United States promises to enable aircraft
to fly closer together and more directly to their destinations due to the real-time positioning
ATCs will now have available at their fingertips. Airlines around the world are already looking
for various ways to conserve fuel: the US-EU Open Skies Agreement allows for direct routes
between foreign countries, and US airlines have formed partnerships like SkyTeam to not only

23. 23
protect against bankruptcy but allow for more direct destinations. With the addition of NextGen,
it is possible that aircraft will be able to fly lower during cruise, more directly between cities, and
reduce fuel expenditure in general.
The problem lies in that this system may have some difficulties before it is ready for
widespread use. A test occurred at Salt Lake City center from March 14-19, 2010 that revealed
instrumentation malfunction and inaccurate data.93
This particular test was run with Lockheed’s
Air-Traffic system that is designed to track 1,900 high-altitude aircraft at a time per twenty
aircraft controllers.94
While this system focuses on the high-altitude aircraft and NextGen
focuses on approaching aircraft, maximum efficiency will not be reached unless the two systems
are working together. As an additional matter, maximum fuel efficiency under current
conditions with current equipment is not going to be enough to reach the goals under Kyoto and
it will only address domestic efficiency. Aircraft fly much higher on trans-oceanic flights (one
pilot reported flying 39,000-40,000 feet over the Atlantic, but only 32,000 feet over the U.S. on
an Airliner.com blog), so while emissions could be reduced over the continental U.S., they
would still be causing the same problems over the ocean.
D. Additional regulation on commercial aircraft operation
Environmental groups and scholars argue that aviation is one of the least regulated
sectors with regard to the environment. Many have recommended placing aircraft as a mobile
source under the Clean Air Act (“CAA”).95
While the author of one such article concedes the
aviation industry is innovating for maximum efficiency and minimum emissions on its own, it
still argues regulation under the CAA may “force these fuel reduction strategies.”96
The question
is how this would fit under the current regulations imposed for commercial aviation.
1. Regulation Effects Under the ICAO Scheme & International Treaty

24. 24
Concededly, regulating aircraft in the United States seems like a quick fix to reduce
emissions from aviation. States have begun regulating with regard to vehicle emissions, why not
aircraft? The unique problem in aviation is its international character. At any given time,
Lufthansa, Air France, Air Italia, British Airways, and Qantas, just to name a few, are operating
over American skies. Additionally, bilateral agreements exist between many of these countries
and the United States in addition to multi-lateral agreements. The ICAO is really the most
reasonable alternative to regulate commercial aviation.
Currently, the ICAO has reduced NOx emissions in commercial aircraft worldwide and
these limits have been codified in the C.F.R. for domestic application. The ICAO meeting next
month will address further emissions cuts that member countries will be required to meet in
order to operate in international skies. Arguably, the current E.U.-ETS conflicts with the EU-US
Open Skies Agreement by requiring US-registered aircraft to report emissions under the EU cap-
and-trade scheme. However, cap and trade is one of the solutions under investigation by the
ICAO. If cap and trade is added next month by the ICAO, the agreements will no longer be in
conflict, but carriers around the world will feel a direct impact from a need to report, limit, and
purchase trading credits to meet international obligations.
2. Regulation Effects Under Current Domestic Law
Under domestic law, the United States has codified its agreements with regard to
commercial aviation. The FAA works with the EPA in promulgating standards so that emissions
reductions are reached without compromising the integrity of the industry. Aircraft cannot be
regulated like automobiles, factories, or businesses. Additionally, the FAA and EPA are
precluded by the ICAO and treaties between other countries. While the United States has some

25. 25
flexibility with regard to domestic safety and efficient routing, the Air Transport Agreement
blocks the “ability to oversee emissions produced by foreign airlines.”97
Regulating under existing domestic environmental schemes for all aircraft is only
possible to the extent that it agrees with the standards set by the ICAO. Any regulation set by the
United States is only going to affect domestic carriers. International carriers will not be
prevented from entering American airspace due to violation of American aviation regulation.
Therefore, the most reasonable solution for attacking the climate change issue within the
regulatory scheme is diligent codification of international agreements with regard to
environmental emissions worldwide.
VI. Conclusion
The aviation industry has certainly come a long way in its 110-year history. It has taken
off from a kite large enough to support one man to a jet powered metal-alloy kite that can carry
300 men halfway around the world. Innovation and research in the industry has led to the advent
of stealth aircraft, regular trips into space, uninhabited aircraft, solar aircraft, and supersonic
fighter jets that reach mach 3 on minimal fuel. Current research for the commercial market
includes the modification of engines to reduce emissions and increase fuel efficiency, alternative
fuels, and GPS air-traffic control systems that will accurately pinpoint an aircraft’s altitude,
speed, and placement to enable controllers to safely and efficiently direct aircraft within their
airspaces.
One solution alone is not going to reduce GHG emissions to the extent needed in light of
the projected growth of the aviation industry and its international obligations. It is likely that a
piece of every system will need to be employed in order to reach environmental goals. For

26. 26
instance, water injection will work to reduce NOx on take-off and climb, but will require
additional fuel due to the added weight. Biofuels blended with synthetic jet fuel could provide a
slightly more sustainable option and reduce carbon emissions, but crop availability is a major
issue. The aircraft can climb to a lower altitude. With the introduction of the NextGen GPS
system and Lockheed’s high-altitude system, air traffic controllers will be able to readily
pinpoint the aircraft to minimize contrail formation and harmful NOx emissions. However,
without modification to the aircraft engine, the lowered altitude will decrease fuel efficiency and
increase NOx and CO2 emissions. Everything comes at a cost.
If the ICAO introduces an international cap-and-trade system with regard to member-
registered aircraft, this could help push the solution in a uniform direction. Enough information
is available for aircraft carriers to determine which methods will be necessary to meet certain
requirements. If high-altitude water emission is the question, aircraft will be required to fly
lower. Water-injection systems are likely to be added to any aircraft making international stops
due to its effectiveness in reducing LTO NOx, smoke, and noise emissions.
Perhaps the most interesting part of the debate is how effectively the industry has already
begun to self-correct. Aircraft did not need to be listed as mobile sources eligible for CAA
regulation in order for carriers and industry professionals to start looking for ways to reduce
emissions and increase fuel efficiency. The fuel efficiency of the average commercial aircraft is
now better overall than the fuel efficiency of an automobile!98
If the industry remains on this
trend, it is likely that the member countries of the ICAO, in conjunction with technical
innovation and support, will reach emissions reduction goals without additional coaxing from
domestic sources.

27. 27
1
Raffi Babikian. The Historical Fuel Efficiency Characteristics of Regional Aircraft from Technological,
Operational, and Cost Perspectives. Masters Thesis. Massachusetts Institute of Technology. June 2001.
p.34.
2
Id. at 41.
3
Michael Gerard Green. Control of Air Pollutant Emissions from Aircraft Engines: Local Impacts of
National Concern. 5 Envtl. Law. 513, 527 (February 1999).
4
David L. Daggett. Water Misting and Injection of Commercial Aircraft Engines to Reduce NOx.
Prepared by Boeing Commercial Airplane Group for the National Aeronautics and Space Administration.
NASA/CR 2004-212957. p.48.
5
Nicolas Eugene Antoine. Aircraft Optimization for Minimal Environmental Impact. Doctoral
Dissertation. Standford University. August 2004. p.27. The take-off and landing cycle (“LTO” involve
four different throttle modes for aircraft are (1) take off: 100% throttle for normally 0.7 minutes, (2)
climb: 85% throttle for 2.2 minutes, (3) approach: 30% throttle for 4 minutes, and (4) idle: 7% throttle for
26 minutes inq2`cluding taxi time.
6
Donald P. Garber, Patrick Minnis, & P. Kay Contulis. A USA Commercial Flight Track Dattabase for
Upper Troposheric Aircraft Emission Studies. NASA Langley Research Center, Atmospheric Sciences.
2003.
7
Michael P. Vanderbergh & Anne C. Steinemann. The Carbon Neutral Individual. Public Law & Legal
Theory Working Paper Number 07-22. Vanderbilt University Law School. 2007. pp.119-20.
8
Allen Pei-Jan Tsai & Annie Petsonk. The Skies: An Airline-Based System for Limiting Greenhouse Gas
Emissions from International Civil Aviation. 6 Envtl. Law. 763, 766 (June 2000).
9
Historical Fuel Efficiency, supra, note 1 at 15.
10
Water Misting and Injection, supra, note 4 at 53. 1999 study showed European Union Urban paid the
most at $60,000 per ton, Swedish 777 emission fee amounted to $52,000 per ton, Southern California
came in at $30,000 per ton, and both the European Union Rural and United States National paid about
$5,000 per ton. One NOx trading credit was about $3,000/ton.
11
Mark L. Schrader. Calculations of Aircraft Contrail Formation Critical Temperatures. Journal of
Applied Meterology. Vol. 36. August 28, 2006 & December 9, 2006. p.1725.
12
Id.
13
See Id. at 1725-1727.
14
Earth Atmosphere Model. NASA – Glenn Research Center. http://www.grc.nasa.gov/WWW/K-
12/airplane/atmos.html.
15
Id.

28. 28
16
USA Commercial Flight Track Database, supra, note 6 at 8.
17
B. Kärcher, Th. Peter & U.M. Biermann, and U. Schumann. The Initial Composition of Jet
Condensation Trails. Journal of Atmospheric Sciences. Vol. 35, No. 21. April 15, 1996. p.3066.
18
Steve S.C. Ou & K.N. Liou. Contrail Cirrus Optics and Radiation. Aviation-Climate Change Research
Initiative – University of California Los Angeles. January 28, 2008. p.10.
http://www.faa.gov/about/office_org/headquarters_offices/aep/aviation_climate/media/ACCRI_SSWP_V
_Ou.pdf.
19
Id. at 14.
20
Id. at 11.
21
Aircraft Optimization, supra, note 5 at 27.
22
Water Misting and Injection, supra, note 4 at 53.
23
Aircraft Optimization, supra, note 5 at 29.
24
Xander Olsthoorn. Carbon Dioxide Emissions from International Aviation: 1950-2050. Journal of Air
Transport Management. Vol 7. 2001. p.87.
25
The Skies, supra, note 8 at 766.
26
Control of Air Pollutant Emissions, supra, note 3 at 520.
27
Id. at 522-23.
28
Alice Bows & Kevin L. Anderson. Policy Clash: Can Projected Aviation Growth be Reconciled with
the UK Government’s 60% Carbon-Reduction Target? Transport Policy. Vol. 14. November 22, 2006.
p.103. Boeing Commercial Airplanes Jet Prices. http://www.boeing.com/commercial/prices/. 2010. A
737-600 ranges from $51.5 million to $58.5 million. The 747-8 ranges anywhere from $293-308 million.
29
Historical Fuel Efficiency, supra, note 1 at 15.
30
Id.
31
Id. at 16. Regional air travel increased 19.7% in 1999 and was anticipated to grow 7.4% annually over
the next ten years. While regional commercial flights perform under 4% of the domestic revenue miles,
they consumed 7% of the jet fuel use and account for 40-50% of total departures.
32
Id. at 15.
33
Policy Clash, supra, note 28 at 103-05.
34
The Skies, supra, note 8 at 767-68.
35
Jessica Finan. A New Flight in the Civil Aviation Industry: The Implications of the United States-
European Union Open Skies Agreement. 17 Tul. J. Int’l & Comp. L. 225, 228 (Winter 2008).

29. 29
36
The Skies, supra, note 8 at 769.
37
Kyoto Protocol, art. 2(2) (1997). The Parties included in Annex I shall pursue limitation or reduction of
emissions of greenhouse gases not controlled by the Montreal Protocol from aviation and marine bunker
fuels, working through the International Civil Aviation Organization and the International Maritime
Organization, respectively. http://unfccc.int/essential_background/kyoto_protocol/items/1678.php.
38
The Skies, supra, note 8 at 769.
39
Id.
40
ICAO Environmental Unit homepage. http://www.icao.int/env. 2010.
41
Id.
42
UNFCCC Copenhagen Convention submission by ICAO. December 7-18, 2009.
http://www.icao.int/env/sbsta-31.pdf. pp.2-3.
43
14 C.F.R. 21.21(b)(1) (2010). In 2011, the new subsection will read “Upon examination of the type
design, and after completing all tests and inspections, that the type design and the product meet the
applicable noise, fuel venting, and emissions requirements of this subchapter, and further finds that they
meet the applicable airworthiness requirements of this subchapter or that any airworthiness provisions not
complied with are compensated for by factors that provide an equivalent level of safety; and (2) For an
aircraft, that no feature or characteristic makes it unsafe for the category in which certification is
requested.”
44
42 U.S.C.A. §7571 (1996). (1) Within 90 days after December 31, 1970, the Administrator shall
commence a study and investigation of emissions of air pollutants from aircraft in order to determine--
(A) the extent to which such emissions affect air quality in air quality control regions throughout the
United States, and (B) the technological feasibility of controlling such emissions. (2)(A) The
Administrator shall, from time to time, issue proposed emission standards applicable to the emission of
any air pollutant from any class or classes of aircraft engines which in his judgment causes, or contributes
to, air pollution which may reasonably be anticipated to endanger public health or welfare. (B)(i) The
Administrator shall consult with the Administrator of the Federal Aviation Administration on aircraft
engine emission standards. (ii) The Administrator shall not change the aircraft engine emission standards
if such change would significantly increase noise and adversely affect safety.
45
14 C.F.R. §34.21 (2009). Engines manufactured after 1997 have CO limits of 118g/kilonewton rO,
after 1999 Nitrogen Oxides are limited to (32 + 1.6 (rPR))g/kN r0.
46
Jessica Finan. A New Flight in the International Aviation Industry: The Imlications of the United
States-European Union Open Skies Agreement. 17 Tul. J. Int’l & Comp. L. 225, 231. (Winter 2008).
47
Id. at 232-35.
48
Air Transport Agreement, art. 15, P2, U.S.-E.U., Apr. 30, 2007, 46 I.L.M. 470 (2007).
49
Policy Clash, supra, note 28 at 108-09.

30. 30
50
Id. Directive 2008/101/EC of the European Parliament (16), November 19, 2008. “In order to avoid
distortions of competition and improve environmental effectiveness, emissions from all flights arriving at
and departing from Community aerodromes should be included from 2012.”
51
EUROPA Environment homepage. http://ec.europa.eu/environment/climat/emission/mrg_en.htm.
February 23, 2010.
52
Directive 2008/101/EC of the European Parliament and of the Council. November 19, 2008. “(3)…
Keeping the 2 °C objective within reach requires stabilisation of the concentration of greenhouse gases in
the atmosphere in line with about 450 ppmv CO2 equivalent, which requires global greenhouse gas
emissions to peak within the next 10 to 15 years and substantial global emission reductions to at least 50
% below 1990 levels by 2050.”
53
See id. at (19).
54
Id. at (18).
55
UK Department for Environment, Food, and Rural Affairs. A Study to Estimate the Impacts of
Emissions Trading on Profits in Aviation. Vivid Economics. January 2008.
http://www.defra.gov.uk/environment/climatechange/trading/eu/future/aviation.htm
56
Water Misting, supra, note 4 at 1-10.
57
Id. at 42.
58
Id. at 43.
59
Id.
60
Id. at 44-46.
61
Id. at 49.
62
Id. at 44-51.
63
Id. at 54.
64
D. Daggett, O. Hadaller, R. Hendricks, & R. Walther. Alternative Fuels and Their Potential Impact on
Aviation. NASA/TM – 2006-214365. p.7.
65
Id. H2 showed roughly 0.75 kg of water, 0.01 kg of CO2, and 2-6g of NOx (depending on combuster) per
10 MJ of fuel whereas kerosene was 0.3 kg of water, 0.75 kg of CO2, and 2-4g of NOx per 10 MJ of fuel.
Methane was a moderate fuel with numbers of 0.4 kg water, 0.6 kg CO2, and 1-3g NOx.
66
Id. at 2.
67
Id. at 3.
68
Id.

31. 31
69
Id.
70
Id. at 4.
71
Id. at 5.
72
Id. at 6.
73
Id.
74
Id.
75
Joan Lowy. Bill Aims to Speed Up Air Traffic Overhaul. Associated Press. March 23, 2010.
http://abcnews.go.com/Business/wireStory?id=10175947
76
Id.
77
Aircraft Optimization. supra, note 5 at 34. Kerosene has the most adverse consequences on relative
GHG at altitudes above 10km (32,808 feet). Reducing the cruise altitude from 11km to 9km cuts the net
impact of NOx emissions in half and severely reduces the likelihood a contrail could form.
78
Id.
79
Id.
80
Historical Fuel Efficiency, supra, note 1 at 27.
81
Id.
82
Air Transport Agreement, art. 15, P2, U.S.-E.U., Apr. 30, 2007, 46 I.L.M. 470 (2007).
83
American Airlines homepage. www.aa.com. 2010. Search was for flights leaving Los Angeles
International on April 24 to Paris, France, and returning on April 26.
84
Air Transport Association Economics and Energy page. Alternative Aviation Fuels Q & A. October 5,
2009. http://www.airlines.org/economics/energy/altfuelsqanda.htm
85
Id.
86
CAAFI homepage & CAAFI News. http://www.caafi.org/about/caafi.html &
http://www.caafi.org/news/CurrentNews.aspx.
87
Aircraft Optimization, supra, note 5 at 53.
88
Id.
89
Id. at 53-55.

32. 32
90
Reduced Verticle Separation Minimum.
http://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/enroute/rvsm/
91
Boeing 767-777. http://www.aa.com/i18n/aboutUs/ourPlanes/boeing777.jsp
92
Boeing MD-80 Stats on American Airlines.
http://www.aa.com/i18n/aboutUs/ourPlanes/boeingMD80.jsp
93
John Hughes. Glitches May Delay Lockheed U.S. Air-Traffic Upgrade, FAA Says. Business Week.
April 9, 2010. http://www.businessweek.com/news/2010-04-09/glitches-may-delay-lockheed-u-s-air-
traffic-upgrade-faa-says.html
94
Id.
95
Daniel H. Conrad. Into the Wild Green Yonder: Applying the Clean Air Act to Regulate Emissions of
Greenhouse Gases from Aircraft. 34 N.C.J. Int’l L. & Com. Reg. 919, 919 (2008-09).
96
Id. at 928-29, 949.
97
A New Flight, supra, note 46 at 237-38. “[A]rticle 15 does not preserve the regulators’ ability to oversee
emissions produced by foreign airlines. This prevents the parties’ regulatory organizations, like the FAA
and EASA, from refusing foreign airlines that are not compliant with their internal standards and
regulations.”
98
Into the Wild Green Yonder, supra, note 95 at 927.