The first F-15A flight was on July 27, 1972. In mid-1979, production F-15As and Bs were superseded on the production lines by the improved single-seat F-15C, with increased internal fuel, totally updated mission avionics, and (Fuel and Sensor) FAST packs, the latter low-drag conformal pallets which attach to the sides of the engine air intake trunk. To fulfill the USAF Enhance Tactical Fighter (ETF) requirement, the F-15E Strike Eagle was developed by McDonnell Douglas and Hughes. This dual-role, two seater fighter, intended for long-range interdiction missions in all weathers, day or night, retains full air-to-air combat capability. The prototype of the airplane first flew in August 1981, and the first new-build F-14E first flew in December, 1986. The USAF was scheduled to receive a total of 1,488 F-15s by the mid-1990s. The F-15C was powered by two 23,930-lb afterburning thrust Pratt & Whitney F100-PW-100 turbofans, giving the airplane a maximum speed (high,clean) Mach 2.5, zoom ceiling 100,000 feet, unrefuelled flight endurance 5 hours 15 minutes. Airplane armament was one M61A1 20-mm six-barrelled cannon and four AIM-9 Sidewinder, four AIM-7 Sparrow or eight AMRAAM air-to-air missiles; in the secondary attack role up to 16,000 lb. of weapons can be carried externally.