High Quality Content by WIKIPEDIA articles! The Lightweight Fighter (LWF) program was a U.S. Air Force technology evaluation program initiated in the 1960s by a cabal of officers and defense analysts known as the "Fighter Mafia". It was spurred by then Major John Boyd`s Energy-Maneuverability (E-M) theory of maneuverability, which indicated that excessive weight would have severely debilitating consequences on the maneuverability of an aircraft. Boyd`s design called for a light-weight fighter with a high thrust-to-weight ratio, a gross weight of less than 20,000 pounds (9,100 kg) (half that of its counterpart, the F-15 Eagle), and high maneuverability. It resulted in the development of the General Dynamics YF-16 and Northrop YF-17. Late in the program, in 1974, with the promise of European sales, the Air Force changed the program name to Air Combat Fighter (ACF), and committed to purchasing 650 models of the YF-16, adopted as the F-16 Fighting Falcon. The U.S. Navy adopted a modified version of the YF-17 as the F/A-18 Hornet.