YF-23 Black Widow II, conducting flight testing somewhere over the Western United States. The Northrop/McDonnell Douglas YF-23 “Black Widow II” was a stealthy, twin-engine fighter prototype built for the USAF’s Advanced Tactical Fighter competition in the late 1980s. Designed to replace the F-15 against advanced Soviet threats, the YF-23 faced off against the Lockheed YF-22. While faster and stealthier, it was less agile, and in 1991 the YF-22 was chosen to become the F-22 Raptor. Only two known