Battles & Wars › World War II › Arsenal of Democracy: US war production
North American Aviation and the P-51 Mustang
designed 1940; ~15,000 built at Inglewood and Dallas· Arms maker, factory or program· Arms makers & war industry
Well documentedSolid records, physical evidence or scientific consensus.
North American Aviation's P-51 Mustang, a long-range fighter that escorted US bombers all the way to Berlin and back.
See it on the Battles & Wars map →What happened
In 1940 Britain asked North American Aviation, led by James 'Dutch' Kindelberger, to build Curtiss P-40s under license; it offered a new design instead, and the prototype rolled out about 100 days after the order. Early Mustangs, with an American Allison engine, were weak at high altitude. Fitted with Britain's Rolls-Royce Merlin, built under license by Packard in Detroit, the P-51B and D were transformed, and drop tanks let them fly from England to Berlin and back. About 15,000 were built.
Why it matters
Escorting bombers deep into Germany, Mustangs helped destroy much of the Luftwaffe's fighter force in early 1944, giving the Allies the air supremacy they needed for D-Day.
How we know
Army Air Forces and company production records, Eighth Air Force combat reports, and many still-flying survivors. Total production figures vary slightly, at about 15,000–16,000.
Still debated
Why the Army Air Forces were slow to see the Mustang's value, first ordering a version as a dive-bomber, is still discussed.
Connections (3)
▸North American Aviation and the P-51 Mustang flew long-range escort for the Strategic bomberWell documented
The connection
US daylight bombers suffered terrible losses over Germany in 1943, as at Schweinfurt in October, because escorts could not go the distance. From December 1943 Merlin-engined P-51s escorted B-17s and B-24s, and by March 1944 they flew with them to Berlin and back. In early 1944 General Jimmy Doolittle freed them to hunt German fighters, wearing down the Luftwaffe.
When and how
Over Germany, December 1943 – 1945; the US Eighth Air Force under General Jimmy Doolittle, and P-51 fighter groups based in England.
How we know
Eighth Air Force loss rates fell sharply in 1944, and German records show heavy fighter-pilot losses that spring.
Debates and open questions
Some historians argue the Luftwaffe's collapse owed as much to fuel shortages and poor pilot training as to Mustang escorts.
▸North American Aviation and the P-51 Mustang helped win the air supremacy needed for D-Day (Normandy landings)Mostly agreed
The connection
In 'Big Week' in February 1944 and the months after, Mustang-escorted bomber raids forced the Luftwaffe to fight and lose pilots it could not replace. On June 6, 1944, the Allies flew about 14,000 sorties over Normandy, while the Luftwaffe managed only a few hundred.
When and how
Over Germany and France, February–June 1944; US Eighth and Ninth Air Forces and RAF fighter units.
How sure are we?
Allied and German sortie counts for June 6, and Luftwaffe pilot-loss records from spring 1944.
Debates and open questions
Credit is shared with other fighters such as the P-47 Thunderbolt and with attacks on German oil; the Mustang's exact share is debated.
▸North American Aviation and the P-51 Mustang shared the Rolls-Royce Merlin engine with the Supermarine Spitfire and its factoriesWell documented
The connection
The Rolls-Royce Merlin powered the Spitfire and Hurricane, but Britain could not build enough of them. Packard in Detroit made Merlins under license from 1941. Fitting a Merlin with a two-stage supercharger to the Mustang in 1942 turned it from a low-level plane into a top high-altitude escort fighter.
When and how
Britain and Detroit, 1941–43; Rolls-Royce, Packard and North American engineers; test conversions at Rolls-Royce's Hucknall airfield in 1942.
How we know
Rolls-Royce and Packard production records; Packard alone built about 55,000 Merlins.
Debates and open questions
Rolls-Royce test pilot Ronnie Harker is usually credited with first suggesting the Merlin Mustang, but American engineers had similar ideas.