The RQ-4 Global Hawk is an unmanned aerial vehicle (UAV) used for surveillance by the United States Air Force and Navy. It can survey up to 40,000 square miles of terrain per day from high altitudes. The aircraft was first flown in 1998 and has undergone several variants for different missions. The Global Hawk uses a single turbofan engine and has a wingspan of over 130 feet, allowing it to reach high altitudes and fly missions up to 28 hours in length with a range of over 8,700 miles.