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 evaluated the YF-17 and was interested in developing a strengthened version capable of carrier operation. Northrop teamed with McDonnell Douglas to develop this new air combat fighter which evolved into the F-18.