The Lockheed Martin/Boeing F-22 Raptor is an American twin-engine, jet-powered, all-weather, supersonic stealth fighter aircraft. As a product of the United States Air Force’s Advanced Tactical Fighter (ATF) program, the aircraft was designed as an air superiority fighter, but also incorporates ground attack, electronic warfare, and signals intelligence capabilities. The prime contractor, Lockheed Martin, built most of the F-22 airframe and weapons systems and conducted final assembly, while program partner Boeing provided the wings, aft fuselage, avionics integration, and training systems. First flown in 1997, the F-22 descended from the Lockheed YF-22 and was variously designated F-22 and F/A-22 before it formally entered service in December 2005 as the F-22A. It replaced the F-15 Eagle in most active-duty U.S. Air Force (USAF) squadrons. Although the service had originally planned to buy a total of 750 ATFs to replace its entire F-15 fleet, it later scaled down to 381, and the program was ultimately cut to 195 aircraft – 187 of them operational models – in 2009 due to political opposition from high costs, a perceived lack of air-to-air threats at the time of production, and the development of the more affordable and versatile F-35 Lightning II. The last aircraft was delivered in 2012.