The United States Air Force (USAF) C-21A is a utility transport aircraft based on the Learjet Model 35A. Designed and manufactured by Learjet in the 1970s, the USAF acquired its first C-21A (modified Learjet 35) in 1984. The agency has been using its twin-engine jet fleet on various missions for four decades. This article notes some fast facts about the USAF C-21A aircraft.