A large number of variants of the General Dynamics F-16 Fighting Falcon have been produced by General Dynamics, Lockheed Martin, and various licensed manufacturers. The details of the F-16 variants, along with major modification programs and derivative designs significantly influenced by the F-16, are described below.
Two single-seat YF-16 prototypes were built for the Light Weight Fighter (LWF) competition. The first YF-16 was rolled out at Fort Worth on 13 December 1973 and accidentally accomplished its first flight on 21 January 1974, followed by its scheduled "first flight" on 2 February 1974. The second prototype first flew on 9 March 1974. Both YF-16 prototypes participated in the flyoff against the Northrop YF-17 prototypes, with the F-16 winning the Air Combat Fighter (ACF) competition, as the LWF program had been renamed.
In January 1975, the Air Force ordered eight full-scale development (FSD) F-16s – six single-seat F-16A and a pair of two-seat F-16B – for test and evaluation. The first FSD F-16A flew on 8 December 1976 and the first FSD F-16B on 8 August 1977. Over the years, these aircraft have been used as test demonstrators for a variety of research, development and modification study programs.