The North American Aviation P-51 Mustangis an American long-range, single-seat fighterand fighter-bomber used during World War II, the Korean War and other conflicts. The Mustang was designed in 1940 by North American Aviation (NAA) in response to a requirement of the British Purchasing Commission for license-built Curtiss P-40 fighters. The prototype NA-73X airframe was rolled out on 9 September 1940, 102 days after the contract was signed and first flew on 26 October.[5][6][7]The Mustang was originally designed to use the Allison V-1710 engine of the P-40, which had limited high-altitude performance. It was first flown operationally by the Royal Air Force(RAF) as a tactical-reconnaissance aircraftand fighter-bomber (Mustang Mk I). The addition of the Rolls-Royce Merlin to the P-51B/C model transformed the Mustang's performance at altitudes above 15,000 ft, matching or bettering that of the Luftwaffe's fighters.[8][nb 1] The definitive version, the P-51D, was powered by the Packard V-1650-7, alicense-built version of the Rolls-Royce Merlin 60 series two-stage two-speed superchargedengine, and armed with six .50 caliber(12.7 mm) M2 Browning machine guns.[10]From late 1943, P-51Bs (supplemented by P-51Ds from mid-1944) were used by theUSAAF's Eighth Air Force to escort bombers in raids over Germany, while the RAF's 2 TAFand the USAAF's Ninth Air Force used the Merlin-powered Mustangs as fighter-bombers, roles in which the Mustang helped ensure Allied air superiority in 1944.[11] The P-51 was also used by Allied air forces in the North African, Mediterranean and Italian theaters, and saw limited service against the Japanesein the Pacific War. During World War II, Mustang pilots claimed 4,950 enemy aircraft shot down.[nb 2]At the start of the Korean War, the Mustang was the main fighter of the United Nationsuntil jet fighters such as the F-86 took over this role; the Mustang then became a specialized fighter-bomber. Despite the advent of jet fighters, the Mustang remai