Northrop YF-23

The Northrop–McDonnell Douglas YF-23 is an American single-seat, twin-engine, stealth fighter prototype technology demonstrator designed for the United States Air Force (USAF). The design team, with Northrop as the prime contractor, was a finalist in the USAF's Advanced Tactical Fighter (ATF) demonstration and validation competition, battling the Lockheed-led YF-22 team for full-scale development and production. Nicknamed "Black Widow II", two YF-23 prototypes were built.

In the 1980s, the USAF began looking for a replacement for its F-15 fighter aircraft to more effectively counter emerging threats such as the Soviet Union's advanced Su-27 and MiG-29 fighters. Several companies submitted design proposals; the USAF selected proposals from Northrop and Lockheed for demonstration and validation. Northrop teamed up with McDonnell Douglas to develop the YF-23, and Lockheed, Boeing, and General Dynamics developed the YF-22. The YF-23 was stealthier and faster, but less agile than its competitor. After a four-year development and evaluation process, the YF-22 team was announced as the winner in 1991 and developed the F-22 Raptor, which first flew in 1997 and entered service in 2005. The US Navy considered using a naval version of the ATF as an F-14 replacement, but these plans were later canceled due to costs.