The Northrop YF-23 or Northrop–McDonnell Douglas YF-23 was an American single-seat, twin-engine fighter aircraft 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 prototypes were built with the nicknames "Black Widow II" and "Gray Ghost".
Its exterior bodywork was made entirely of titanium(which turned out to be hard to make). The engine output was 200 hp (150 kW), and to solve the exhaust heat problem it was fed through a regenerative system, which allowed the entire engine to operate at nearly 1,000 °F (538 °C) cooler, and also power the accessories. Kerosene was the most common fuel used Another innovation on the car was the first use of four wheel disc brakes, with a fully independent suspension, as well as a sophisticated guidance system which was intended to be used with "the highway of the future", where an electrical wire would be embedded into a roadway to send signals that would help guide future cars and avoid accidents.
The Sukhoi PAK FA is a twin-engine jet fighter being developed by Sukhoi for the Russian Air Force. The Sukhoi T-50 is the prototype for PAK FA. The first flight of the PAK FA was performed on 29th of January, 2010. The serial production is expected to start in 2015.
The plane was designed to replace Su-27 for the Russian Air Forces. They are also developing an export modification together with India, it is called FGFA – Fifth Generation Fighter Aircraft.