North American P-51 Mustang
The P-51 Mustang is an American single-seat, long-range fighter and fighter-bomber of the Second World War, also flown in the Korean War. North American Aviation designed it to a British order in 1940, and it became a different class of aircraft once the Rolls-Royce Merlin replaced its original Allison engine: with external tanks it could escort heavy bombers deep into Germany and back. Production across all variants is reported at 15,686, and the type went on to serve air forces around the world for decades after 1945.
Why It Mattered
The Mustang mattered because it gave the Allied bomber offensive a fighter that could accompany bombers on missions deep inside Germany and still fight effectively at the far end of the route. It matured into a long-range escort that could also strafe ground targets and fly photographic reconnaissance. That versatility made the type as valuable against ground targets as it was against fighters. When Merlin-powered Mustangs arrived in numbers in 1944, the Eighth Air Force regained the confidence to strike deep, with escorts that stayed for the whole mission.
Design Notes
The Mustang is a single-engine, low-wing monoplane built around a liquid-cooled inline engine. The decisive change was an engine swap: a British initiative endowed the Mustang with the Rolls-Royce Merlin, whose two-stage, two-speed supercharger held its power at high altitude. The definitive P-51D used the Packard V-1650-7, the Merlin built under license in the United States, and the Merlin installation made the fighter about 50 mph faster than previous models. With external fuel tanks fitted, a Mustang could fly more than 2,000 miles without refueling, a reach few single-seat fighters could approach. The P-51D also introduced a bubble canopy for better visibility and carried six .50-caliber machine guns. The liquid-cooled engine was also the type's weak point: a single bullet through a radiator or coolant pipe could bring a Mustang down.
Operational History
The Mustang first flew in October 1940, and the Royal Air Force (RAF) took its first Mustang squadrons into service in January 1942. When Merlin-powered Mustangs arrived in numbers in 1944, the Eighth Air Force gained the confidence to strike deep into Germany again. With escorts able to stay with the bombers for the entire mission, the daylight campaign deep into Germany could be sustained. That year, American fighter squadrons were ordered to hunt the German interceptors rather than hold close formation with the bombers, and Mustang victories rose. In the Pacific, Mustangs based on Iwo Jima escorted B-29 Superfortresses on long-range bombing attacks against Japan. Redesignated the F-51, the Mustang returned to combat in the Korean War on close-support and ground-attack work, dangerous low-level missions for an aircraft with a vulnerable cooling system. The U.S. Air Force did not finally withdraw the type from service until 1957.
Afterlife
Production across all variants is reported at 15,686 aircraft, and surplus Mustangs passed to air forces around the world, some of which kept the type in service for decades. The last military operator, the Dominican Air Force, is reported to have retired its Mustangs in 1984, nearly four decades after the type's wartime peak. In civilian hands, Mustangs became fixtures of air racing, the Reno Air Races among them, and of the warbird circuit, where restored examples remain among the most widely recognized survivors of the Second World War. National museums hold other survivors; the Smithsonian's own P-51D, built in 1945, never saw combat.