Development of the single engine aircraft began in 1943, based on the British H-1-B-jet engine. The P-80 had an all-metal fuselage design. The first prototype was flown under the callsign XP-80 on 8th January 1944, with a Halford H1 engine (later called the “Goblin”), which was removed from a de Havilland Vampire and sent to the USA, because the first engine was destroyed in an accident. The new aircraft was able to reach a speed of 808 km/h. Because de Havilland was unable to built enough engines for operational P-80 Shooting Stars, the company Allis-Chalmers started building them under license, but this didn't work out. Lockheed then built the Whittle I-40 under license. However, because the new engine was larger than the H-1 engine, the fuselage of the P-80 had be enlarged as well.