The North American Air Force P-51 Mustang is an American long-range single-seat fighter and fighter-bomber that was used during World War II and the Korean War, among other conflicts. The Mustang was developed in April 1940 by a team led by James H. Kindelberger of North American Aviation (NAA) in response to a request from the British Procurement Commission. The commission asked the NAA to build Curtiss P-40 fighters under license for the Royal Air Force (RAF). Instead of building another company's old design, NAA proposed to design and manufacture a more modern fighter. The NA-73X airframe prototype was released on September 9, 1940, 102 days after the contract was signed, and the first flight took place on October 26. The Mustang was designed to use the Allison V-1710 engine without an export-sensitive turbocharger or multi-stage supercharger, which limited high-altitude performance. The aircraft was first adopted by the Royal Air Force as a tactical reconnaissance aircraft and fighter-bomber (Mustang Mk I). The replacement of the Allison with a Rolls-Royce Merlin two-stage supercharged engine resulted in the P-51B/C (Mustang Mk III) model and changed the aircraft's performance at altitudes above 15,000 ft (4,600 m) (without loss of range), allowing it to compete with Luftwaffe fighters . The final version, the P-51D, was equipped with the Packard V-1650-7, a licensed version of the two-speed, two-stage supercharged Merlin 66, armed with six .50 (12.7 mm) AN/M2 Browning machine guns. From late 1943, P-51Bs and P-51Cs (supplemented by P-51Ds from mid-1944) were used by the US Eighth Air Force to escort bombers during raids over Germany, while the Royal Air Force's Second Tactical Air Force and Ninth Air Force The USAF used Merlin-powered Mustangs as fighter-bombers, in which the Mustang helped secure Allied air superiority in 1944. The P-51 was also used by Allied air forces in North Africa, the Mediterranean, Italy, and the Pacific. During World War II, Mustang pilots claimed to have destroyed 4,950 enemy aircraft. At the start of the Korean War, the Mustang, by then redesignated the F-51, was the United States' primary fighter until jet fighters, including the North American F-86, took over that role; Mustang became a specialized fighter-bomber. Despite the advent of jet fighters, the Mustang remained in service with some air forces until the early 1980s. After the Korean War, Mustangs became popular civilian combat aircraft and air racing aircraft.
