The doctrine of daylight precision bombing was at the core of military thinking and planning among the most powerful group of USAAF generals and thinkers in the prewar days of the late 1930s, many of them mentored by General Billy Mitchell and adherents to the writings and predictions of Alexander de Severski and others. Across the Atlantic where an independent Royal Air Force had already had its birth there was a similar cadre known as “the bomber boys”. In both cases a lot of water and flying miles separated them from likely foes and multi-engine warplanes were a natural industrial component of military thinking and developing manufacturing capacity.
Most of these thinkers were beguiled however by the belief that no matter what, “the bombers would always get through”; that protected by altitude and the combined defensive fire power of their own heavy weapons systems they would be able to survive fighter attack and ground fire. RAF bomber command had already learned the fallacy of this thinking. At high altitude they couldn’t hit the targets while they paid a high price in men and aircraft to both flak and enemy fighters; they had long since gone to night-time bombing and from lower altitudes. The Americans would learn the same lesson at a high price right up to the disastrous Schweinfurt/Regensburg raids of 1943 (the straw that finally broke the “8th Air Force back”.) What was needed was a fast, long range, high-altitude fighter capable of protecting the bomber formations all the way to the targets and back. Something the vaunted Spitfire, Hurricane and even Thunderbolt couldn’t do.
The story of the P-51 Mustang begins in the British anxieties about a European war in 1939, when that country’s air ministry approached North American Aviation with the intent of ordering a number of Curtis P-40s to be built to augment the Spitfire/Hurricane inventory. Noting that the P-40 design was already an out-dated one, “Dutch” Kindelberger of North American proposed coming up with a totally new fighter his company might build. Given only 120 days to produce a test model, necessitating a few temporary adjustments, the first prototype NA X-51 first flew on Oct. 26, 1940. It would eventually out-perform the Spitfire. The laminar flow wings would produce a higher speed and greater range than any contemporary fighter, even with the specified Allison V-1710-39 engine which turned out not to be a good match. The Allison was a fine engine by the way, and performed well in the P-38 Lightning. The Brits were sufficiently impressed to initially order 620 of these planes. But the first P-51s did not perform well enough when compared to the German Bf-109 and FW-190 at altitude. British test pilot Ronnie Harker was asked to fly the plane before the decision would be made to scrap the order. In the process, he measured the engine compartment and discovered it was an exact match for the Rolls Royce Merlin power plant which was the mainstay for the Spitfire, Hurricane, Mosquito and most British bombers. Wind tunnel tests bore out Harker’s prediction that the Mustang when matched up with the Merlin would be superior in performance at any altitude over any other fighter then flying. And with wing tanks then coming on line, it could protect the B-24s, B-17s and Lancasters to Berlin and back! Harker would be one of the plane’s saviors.
The real problem was political. The Mustang was a “hybrid”: Built in America, but designed and developed to British specs.. The USAAF and its purchasing bureau were committed to the P-47 Thunderbolt, the P-38 Lightning and the (worthless) P-39 Airacobra platforms along with the industrial giants awaiting those orders. And then there was the Rolls Royce engine, intrinsic to the final design and the heart of the plane’s extraordinary performance, but whose manufacturing capacity was needed to support nearly all the warplanes England would be flying for the duration of the war. Both countries needed the Mustang, but neither wanted the other to have the credit for coming up with it!
Thanks only to a small handful of patriotic middle-level officers and supporters (and the quiet intervention of Roosevelt and Churchill,) did the USAAF avoid making the costliest mistake of WWII. In the end the Packard Motor Car Co. was licensed to manufacture the fabled Rolls Royce Merlin engine in the U.S., and American industrial genius was able to send 14,819 Mustangs to change the balance of air power in the skies over Europe and all the way to the Japanese surrender in the Pacific.
A North American P-51D Mustang with tear-drop canopy and dorsal fin.