 {| |} the lockheed/boeing/general dynamics yf-22 was a single-seat, twin-engine fighter aircraft technology demonstrator designed for the united states air force (usaf). the yf-22 was a finalist in the usaf's advanced tactical fighter competition, and two prototypes were built for the demonstration/validation phase of the competition. the yf-22 won the contest against the northrop yf-23, and entered production as the lockheed martin f-22 raptor. the yf-22 is aerodynamically similar to the f-22, but with differences in the position and design of the cockpit, tail fins and wings, and in internal structural layout. in the 1980s, the usaf began looking for a replacement for its fighter aircraft, especially to counter the advanced su-27 and mig-29. a number of companies, divided into two teams, submitted their proposals. northrop and mcdonnell douglas submitted the yf-23. lockheed, boeing and general dynamics proposed and built the yf-22, which, although marginally slower and having a larger radar cross-section, was more agile than the yf-23. primarily for this reason, it was picked by the air force as the winner of the atf in april 1991. following the selection, the first yf-22 was retired to a museum, while the second prototype continued flying until an accident relegated it to the role of an antenna test vehicle. == design and development ==  in 1981, the u.s. air force developed a requirement for an advanced tactical fighter (atf) as a new air superiority fighter to replace the f-15 eagle and f-16 fighting falcon. this was made more crucial by the emerging worldwide threats, including development and proliferation of soviet mig-29 and su-27 "flanker"-class fighter aircraft. it would take advantage of the new technologies in fighter design on the horizon including composite materials, lightweight alloys, advanced flight-control systems, more powerful propulsion systems and stealth technology.{{cite web|title=fact sheet: lockheed-boeing-general dynamics yf-22|publisher=u.s. air force|date
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