 The sale included five E-3 Sentry AWACS aircraft and eight KE-3 refueling aircraft, with spare parts and support, delivered between June 1986 and September 1987.The United States Air Force began using the E-3 Airborne Warning and Control System aircraft in 1977 following ten years of prototype design, development, and testing.The U.S. currently has a fleet of 32 E-3s, the largest in the world.