"The P-51 Mustang is arguably the greatest fighter of all time. With its long range, superior speed, lethal weaponry and outstanding maneuverability, the Mustang proved to be unequalled as an escort fighter. It was also an outstanding interceptor and ground attacker as well as reconnaissance aircraft. The fact that the Mustang remained in service with various air forces around the world in the 1980's is a testament to its abilities"
The superior characteristics and longevity of the Mustang are a hallmark to the design created by North American Aviation. A company that had never before designed a fighter aircraft, NAA made the Mustang from conception to prototype in an unprecedented 120 days.
The P-51 began its career because of the British considering NAA as a potential supplier of the Curtis P-40. Rather than build someone else's airplane, North American's Raymond Rice and Edgar Schmued wanted instead to create their own. The British agreed to let the company try; provided it could produce a prototype within 120 days. NAA made the deadline and the prototype, called the NA-73, made its maiden flight on October 26, 1940.
The Mustang was a very advanced design with its laminar flow wing and other innovative features such as a centrally located radiator scoop and airflow ducting which combined to make it highly effective in many regimes. Initial flights exposed some minor problems primarily related to engine overheating, but it did not take long for the designers to confirm what they suspected: The NA-73X was a highly advanced fighter and represented a major breakthrough in fighter design.
The British did not need to wait until October to realize the potential of this new fighter. In late May they ordered 320 of the unproven and unfinished design. Under this contract, two of the fighters were to be given to the USAAF for testing. The designation of these of these American aircraft was XP-51.
Surprisingly, while the British anxiously awaited delivery of their new fighter, the USAAF all but ignored it while focusing on the P-38 Lighting and P-47 Thunderbolt. Meanwhile the British, while happy with the low altitude performance, were less than thrilled with the performance as the Allison powered Mustang passed 17,000 feet. In an effort to remedy this they attempted a marriage of the Mustang airframe with a Rolls-Royce Merlin Engine. The result astonished test pilots and they knew they had a truly advanced fighter on their hands. This is the Rolls-Royce powered Mustang that became the P-51 as we know it today.