The Northrop/McDonnell Douglas YF-23 is an American single-seat, twin-engine 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 prototypes were built, nicknamed "Black Widow II" and "Gray Ghost".

In the 1980s, the USAF began looking for a replacement for its fighter aircraft, especially to 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 entered production as the Lockheed Martin F-22 Raptor. 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. The two YF-23 prototypes are currently museum exhibits.
The first YF-23, with Pratt & Whitney engines, supercruised at Mach 1.43 on 18 September 1990, while the second, with General Electric engines, reached Mach 1.6 on 29 November 1990. By comparison, the YF-22 achieved Mach 1.58 in supercruise. The YF-23 was tested to a top speed of Mach 1.8 with afterburners and achieved a maximum angle-of-attack of 25°. The maximum speed is classified, though sources state a maximum speed greater than Mach 2 at altitude and a supercruise speed greater than Mach 1.6. The aircraft's weapons bay was configured for weapons launch, and used for testing weapons bay acoustics, but no missiles were fired; Lockheed fired AIM-9 Sidewinder and AIM-120 AMRAAM missiles successfully from its YF-22 demonstration aircraft. PAV-1 performed a fast-paced combat demonstration with six flights over a 10-hour period on 30 November 1990. Flight testing continued into December. The two YF-23s flew 50 times for a total of 65.2 hours. The tests demonstrated Northrop's predicted performance values for the YF-23. The YF-23 was stealthier and faster, but the YF-22 was more agile.
A YF-22 in the foreground with a YF-23 in the background

The two contractor teams submitted evaluation results with their proposals in December 1990, and on 23 April 1991, Secretary of the Air Force Donald Rice announced that the YF-22 was the winner. The Air Force selected the YF119 engine to power the F-22 production version. The Lockheed and Pratt & Whitney designs were rated higher on technical aspects, were considered lower risks, and were considered to have more effective program management. It has been speculated in the aviation press that the YF-22 was also seen as more adaptable to the Navy's NATF, but by 1992 the U.S. Navy had abandoned NATF.

Following 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.

The Lockheed/Boeing/General Dynamics YF-22 is an American single-seat, twin-engine fighter aircraft technology demonstrator designed for the United States Air Force (USAF). The design 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 has a similar aerodynamic layout and configuration as the F-22, but with differences in the position and design of the cockpit, tail fins and wings, and in internal structural layout.
The YF-22 was designed to meet USAF requirements for survivability, supercruise, stealth, and ease of maintenance. Because Lockheed's submission was selected as one of the winners, the company, through its Skunk Works division, assumed leadership of the program partners. It would be responsible for the forward cockpit and fuselage, as well as final assembly at Palmdale, California. Meanwhile, the wings and aft fuselage would be built by Boeing, with the center fuselage, weapons bays, tail and landing gear built by General Dynamics. Compared with its Northrop/McDonnell Douglas counterpart, the YF-22 has a more conventional design – its wings have larger control surfaces, such as full-span trailing edge, and, whereas the YF-23 had two tail surfaces, the YF-22 had four, which made it more maneuverable than its counterpart. Two examples of each prototype air vehicle (PAV) were built for the Demonstration-Validation phase: one with General Electric YF120 engines, the other with Pratt & Whitney YF119 engines.

The YF-22 was given the unofficial name "Lightning II" after Lockheed's World War II-era fighter, the P-38 Lightning, which persisted until the mid-1990s when the USAF officially named the aircraft "Raptor". The F-35 later received the "Lightning II" name in 2006.

The first YF-22 (PAV-1, serial number 87-0700, N22YF), with the GE YF120, was rolled out on 29 August 1990 and first flew on 29 September 1990, taking off from Palmdale piloted by David L. Ferguson. During the 18-minute flight, PAV-1 reached a maximum speed of 250 knots (460 km/h; 290 mph) and a height of 12,500 feet (3,800 m), before landing at Edwards AFB. Following the flight, Ferguson said that the remainder of the YF-22 test program would be concentrated on "the manoeuvrability of the aeroplane, both supersonic and subsonic". The second YF-22 (PAV-2, s/n 87-0701, N22YX) with the P&W YF119 made its maiden flight on 30 October at the hands of Tom Morgenfeld.

During the flight test program, unlike the YF-23, weapon firings and high (60°) angle of attack (AoA, or high-alpha) flights were carried out on the YF-22. Though not a requirement, the aircraft fired AIM-9 Sidewinder and AIM-120 AMRAAM missiles from internal weapon bays. Flight testing also demonstrated that the YF-22 with its thrust vectoring nozzles achieved pitch rates more than double that of the F-16 at low-speed maneuvering. The first prototype, PAV-1, achieved Mach 1.58 in supercruise, while PAV-2 reached a maximum supercruise speed of Mach 1.43; maximum speed was in excess of Mach 2.0. Flight testing continued until 28 December 1990, by which time 74 flights were completed and 91.6 airborne hours were accumulated. Following flight testing, the contractor teams submitted proposals for ATF production.

On 23 April 1991, the YF-22 was announced by Secretary of the Air Force Donald Rice as the winner of the ATF competition.[21] The YF-23 design was stealthier and faster, but the YF-22 was more agile.[22] It was speculated in the aviation press that the YF-22 was also seen as more adaptable to the Navy's Navalized Advanced Tactical Fighter (NATF), but the US Navy abandoned NATF by 1992.[16][23] Instead of being retired, as with the case of PAV-1, PAV-2 subsequently flew sorties following the competition – it amassed another 61.6 flying hours during 39 flights.[16] On 25 April 1992, the aircraft sustained serious damage during a landing attempt as a result of pilot-induced oscillations. It was repaired but never flew again, and instead served as a static test vehicle thereafter.[24][25] In 1991, it was anticipated that 650 production F-22s would be procured.

As the Lockheed team won the ATF competition, it was awarded the engineering, manufacturing and development (EMD) contract, which would ultimately allow it to proceed with production of operational aircraft. The EMD called for seven single-seat F-22A and two twin-seat F-22Bs. On 9 April 1997, the first of these, Spirit of America, was rolled out. During the ceremony, the F-22 was officially named "Raptor". Due to limited funding, the first flight, which had previously been scheduled for mid-1996, occurred on 7 September 1997. Flight testing for the F-22 continued until 2005, and on 15 December 2005 the USAF announced that the Raptor had reached its initial operational capability (IOC).

In many respects, the YF-22s were different from production F-22s. Contrary to the F-117 Nighthawk, which was initially difficult to control because of small vertical stabilizers, Lockheed over-specified the fin area on its YF-22. Therefore, the company reduced the size of those on F-22s by 20–30 percent. Lockheed recontoured the shape of the wing and stabilator trailing edges to improve aerodynamics, strength, and stealth characteristics; the wing and stabilitor sweep was reduced by 6° from 48°. Finally, to improve pilot visibility, the canopy was moved forward 7 inches (178 mm), and the engine intakes were moved rearward 14 inches (356 mm)