Northrop YF-17Northrop YF 17 airplane model. In 1972, the USAF sought proposals for a new fighter under the Lightweight Fighter (LWF) program. The LWF prototype program called for a small, lightweight, low cost, air superiority day fighter designed for high performance and ease of maintenance. The Northrop YF 17 was tested against the General Dynamics YF 16 in the LWF fly off competition. The F 16 won and entered production starting in 1975. The US Navy also