The Northrop/McDonnell Douglas YF-23 is an American single-seat, twin-engine, supersonic stealth fighter aircraft technology demonstrator designed for the United States Air Force (USAF). The design was a finalist in the USAF's Advanced Tactical Fighter (ATF) competition, battling the Lockheed YF-22 for a production contract. Two YF-23 prototype air vehicles were built.
In the 1980s, the USAF began looking for a replacement for its fighter aircraft to more effectively counter the USSR's advanced Sukhoi Su-27 and Mikoyan MiG-29. Several companies submitted design proposals; the USAF selected proposals from Northrop and Lockheed. Northrop teamed with McDonnell Douglas to develop the YF-23, while 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 was announced the winner in 1991 and developed into the Lockheed Martin F-22 Raptor, which first flew in 1997 and entered service in 2005. The U.S. Navy considered using the production version of the ATF as the basis for a replacement to the F-14, but these plans were later canceled. TFollowing the competition, both YF-23s were transferred to NASA's Dryden Flight Research Center at Edwards AFB, California, without their engines. NASA planned to use one of the aircraft to study techniques for the calibration of predicted loads to measured flight results, but this did not take place. Both YF-23 airframes remained in storage until mid-1996, when the aircraft were transferred to museums. At the museums, the planes underwent restoration, during which it is believed that the aircraft's callsigns were switched. PAV-1 received "Gray Ghost" on the underside of its landing gear cover, while PAV-2 had "Spider" painted in the same location.