This document discusses mapping air population by tracking real-time flight data. It defines air population as the total number of people flying above the earth at a given time, which fluctuates daily. The authors created animated maps in 2007 showing North American flight patterns over time. They now retrieve live flight data from tracking companies to map current air traffic and calculate air population densities and ratios compared to ground populations for different states and times of day. Their implementation uses a database and ArcGIS API to spatially analyze and visualize the flight data on interactive maps.