In April 1940, drawings were sketched in a New York City hotel room for a new fighter aircraft for the British purchasing Commission. This fighter, the North American NA73X, became one of the best fighter aircraft in the U.S. Army Airforce during World War II, and is known as the P-51 Mustang.

Of the several variations of this famous fighter, the P-51D is generally accepted as the definitive Mustang and was the first production version with the "Bubble" canopy. More "D" model Mustangs were built than all other Mustang variants combined, with a total of 9,603 coming off production lines. 45 squadrons of the famed U.S. 8th Airforce, stationed in England were equipped with the P-51D, which could now escort and protect the heavy bombers all the way to and from targets on the European continent.