The Lockheed Martin YF-22 won the Air Force's Advanced Tactical Fighter (ATF) contest over the Northrop YF-23 in April 1991. In 1983 the Air Force had issued a request for proposals for the ATF program, which were based on a study on new fighter concepts. The F-22 program is developing the next-generation air superiority fighter for the United States Air Force to ensure it retains it's air dominance and can counter emerging worldwide threats.