Lord Ellpus wrote:Plus they nicked most of our Spitfire (and admittedly developed a far superior plane)
False, the P51 (Pursuit Aircraft model 51) was developed from prototypes which were begun in 1939. In 1940, North American Aviation signed a contract with the Brits to develop a fighter aircraft which would carry eight heavy machine guns. The United States Army Air Force reluctantly agreed to the contract, but the North American prototype, NA-73X, was rejected by the Brits, largely because they considered it to be "underpowered." North American continued to develop the aircraft which would become the P51 Mustang, though, as a ground support fighter, and it was a superior plane for that purpose even in its final form. But the Pratt and Whitney in-line engine was not powerful enough for the aircraft to perform with contemporary fighters. It is false that the design was based on any Supermarine models, because even though the Spitfire was known in 1939, it's design specifications were classified by the British, and were not given to North American.
The great breakthrough was acheived when Imperial General Staff air officers suggested that the North American NA-73X might benefit from using the Rolls Royce Merlin engine. It was fuel-injected and in every other way superior to any existing in-line engine. It made the Mustang the greatest propellor driven aircraft ever to fly.
Chuck Yeager, a fighter ace and test pilot well known to Americans once said in a television interview that what the Spitfire could do for 40 minutes, the Mustang could do for eight hours. The Mustang was better armed (eight 50 cal. machine guns), better armored, roomier and carried far more fuel than the Spitfire, which could only operate locally as an air defense fighter. Adolph Galland, head of the Luftwaffe fighter arm at the end of the war, tells in his war memoir how Mustangs would follow German aircraft back to their bases when they (the Germans) were running out of fuel, and shoot up everything in sight. By the end of the war, German fighters were flying out of logging roads in forests.