The McDonnell XF-88 Voodoo was a long-range, twinjet fighter aircraft with swept wings designed for the United States Air Force. Although it never entered production, its design was adapted for the subsequent supersonic F-101 Voodoo.
The Consolidated Vultee XP-81 is a development of the Consolidated Vultee Aircraft Corporation to build a single seat, long range escort fighter that combined use of both turbojet and turboprop engines. Although promising, the lack of suitable engines combined with the end of World War II doomed the project.
The Vultee P-66 Vanguard was a United States Army Air Forces fighter aircraft. It was initially ordered by Sweden, but by the time the aircraft were ready for delivery in 1941, the United States would not allow them to be exported, designating them as P-66s and retaining them for defensive and training purposes. Eventually, a large number were sent to China where they were pressed into service as combat aircraft with mixed results.
The Curtiss P-60 was a 1940s American single-engine single-seat, low-wing monoplane fighter aircraft developed by the Curtiss-Wright company as a successor to their P-40. It went through a lengthy series of prototype versions, eventually evolving into a design that bore little resemblance to the P-40. None of these versions reached production.
The Curtiss XP-62 was a prototype single-engine interceptor aircraft, that was built for the United States Army Air Forces, by the Curtiss-Wright Corporation. It first flew in 1943.
The Lycoming XR-7755 was the largest piston aircraft engine ever built in the United States, with 36 cylinders totaling about 7,750 in3 (127 L) of displacement and a power output of 5,000 horsepower (3,700 kilowatts). It was originally intended to be used in the "European bomber" that eventually emerged as the Convair B-36. Only two examples were built before the project was terminated in 1946.
The Grumman XP-50 was a land-based development of the shipboard XF5F-1 Skyrocket fighter, entered into a United States Army Air Corps (USAAC) contest for a twin-engine heavy interceptor aircraft. The USAAC placed an order for a prototype on 25 November 1939, designating it XP-50, but it lost the competition to the Lockheed XP-49.
The Lockheed XP-58 Chain Lightning was an American long-range fighter developed during World War II. Although derived from the successful P-38 Lightning, the XP-58 was plagued by technical problems with its engines that eventually led to the project's cancellation.
The Republic XP-72 was an American prototype fighter-interceptor developed by Republic Aircraft as a progression of the P-47 Thunderbolt design. The XP-72 was designed around the Pratt & Whitney R-4360 Wasp Major 28-cylinder air-cooled radial engine with a supercharger mounted behind the pilot and driven by an extension shaft from the engine. The armament consisted of six .50 caliber (12.7 mm) wing-mounted Browning AN/M2 machine guns and underwing racks for two 1,000 lb bombs; Alternative armament packages included two 37 mm M4 autocannons with four .50 caliber AN/M2s, or four M4 autocannons.
The Republic XP-69 was an American fighter aircraft proposed by Republic Aviation in 1941 in response to a requirement by the United States Army Air Corps for a high-speed fighter. Manufacturers were encouraged to consider unorthodox designs; although the design was ordered as a prototype it was canceled because of delays with the engine that was to power it.
The Vultee XP-54 Swoose Goose was a prototype fighter built by the Vultee Aircraft Company for the United States Army Air Forces (USAAF).
The Hawker Tornado was a British single-seat fighter aircraft design of the Second World War for the Royal Air Force as a replacement for the Hawker Hurricane. The planned production of Tornados was cancelled after the engine it was designed to use, the Rolls-Royce Vulture, proved unreliable in service. A parallel airframe that used the Napier Sabre engine continued into production as the Hawker Typhoon.
The Curtiss XP-71 was a 1941 American proposal for an exceptionally large heavy fighter design. It was intended to serve as an extreme-range interceptor and escort fighter. While significant progress was made in the design phase, no prototypes were ever built, and the design was abandoned in 1943.
The Consolidated P-30 (PB-2) was a 1930s United States two-seat fighter aircraft. An attack version called the A-11 was also built, along with 2 Y1P-25 prototypes and YP-27, Y1P-28, and XP-33 proposals. The P-30 is significant for being the first fighter in United States Army Air Corps service to have retractable landing gear, an enclosed and heated cockpit for the pilot, and an exhaust-driven turbo-supercharger for altitude operation.
The XP-13 Viper was a prototype biplane fighter aircraft designed by the American company Thomas-Morse Aircraft Corporation. The airplane was delivered to the United States Army in 1929, but they did not adopt it.
The Berliner-Joyce P-16 was a 1930s United States two-seat fighter aircraft produced by Berliner-Joyce Aircraft Corporation.
The Wright R-2160 Tornado was an experimental 42-cylinder, 7-cylinder per row, 6-row liquid-cooled inline radial aircraft engine. It was proposed in 1940 with 2,350 hp (1,752 kW) for experimental aircraft such as the Lockheed XP-58 Chain Lightning, Vultee XP-68 Tornado, and the Republic XP-69.
The Curtiss XP-31 Swift was a 1930s American experimental monoplane fighter built by Curtiss for the United States Army Air Corps.
The Mitsubishi J4M Senden or Navy Experimental 17-Shi Otsu B Type Interceptor Fighter Senden, Allied reporting name Luke, was a Japanese World War II fighter aircraft proposed by Mitsubishi Heavy Industries for use by the Imperial Japanese Navy. The J4M project did not proceed beyond the design stage.
The Mansyū Ki-98,, was a Japanese ground-attack aircraft proposed by Mansyū during World War II for use by the Imperial Japanese Army Air Force. The still unassembled components of the first prototype were deliberately destroyed before Japan surrendered.
