At the time when North American was producing the B-25 Mitchell bomber and the T-6 Texan trainer, (both are radial engine aircraft) the British (RAF) requested a fighter design. Out pops the Mustang, in 1940. Yes, it took a few years and the Rolls Royce Merlin engine for the aircraft to reach it's potentional, but by 1940 standards the Mustang was a fantastic leap in aviation technology.
In the opinion of many, the P-51 Mustang was the best fighter of WWII. Although I prefer my aircraft to have BIG round engines, the Mustang is quite a fighter.
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