North American P51D Mustang owed legendary reputation and success to its equally matched capabilities as a military multi-role aerial fighter craft and these characteristics were the result of a successful design by North American Aviation designers Raymond Rice and Edgar Schmued. The design originated in the British Royal Air Force requirement of a number of additional Curtiss P-40 fighter aircraft, it forced the British to consider NAAs manufacturing capacity. The pair of NAA designers saw this as a potential prospect to design and produce an entirely new aerial fighter, seizing this opportunity they drew up a new design proposal for review by the British forces. Their design was well received and accepted under a latter-day 1940 performance specification was looking to procure a fighter showing an excellent turn of speed whilst heavily armed at the then extreme altitudes at which heavy bomber flight operations took place.
The British accepted with the understanding that a fully operational prototype be readied for test flights inside a 120 day period. The manufacturer met the goal and provided a working prototype, the NA-73X within just 102 days, its first test flight occurred on 26 October 1940 while fitted with the Allison V-1710-F3R in-line piston engine developing 1100 hp. The prototype immediately showed tremendous military potential as a fighter and the impressed British forces place an order for 320 of the new Mustang I air fighters. Mustang I fighters first took to the British skies with local pilots at the stick on 1 May 1941, by then the aircraft were considered to be quite modestly armed by its four x 12.7 mm calibre fully automatic machine guns, these first delivered aeroplanes were to be deployed to serve as tactical reconnaissance aircraft.
The Mustang I displayed remarkably good low-level responses and performance in some areas even outperforming, the by now much loved, Spitfire Mk V, it however showed a significant drop off in performance at altitudes over 15,000 feet. Resultantly, British Army Co-Operation Squadrons was on the fortunate receiving end of the new Mustang I air fighters, where they were deployed in either a high-speed ground attack or alternatively in a low-level reconnaissance aircraft role. The Mustang I successfully concluded its first British operational attack mission on 10 May 1942 when 26 Squadron strafed German aircraft hangers located in Berck sur Mer, an area in France then under German military occupation. The British forces with the receivers of the greater part of the Mustang Mk IA early production runs eventually taking possession of 620 standard production aircraft.
The US Air Force soon noticed the new Mustangs and took receipt of two models for evaluation purposes with these given the model designation XP-51, the USAAF found them to be excellent during testing but did not commit to an order at that time. Fortunately due to General Hap Arnold’s intervention 55 of these Britain bound Mk IA Mustangs were held for American service duties, which were to become reconnaissance aircraft bearing the F-6A model designate and also be the first American Mustang served squadrons. It went on to a total production quantity of 15,469 Mustangs of all variants completed by 1946. The Mustang P-51 shown impressive range and performance and exceeded all expected specification levels, in aerial combat its numbers and competency forced a definitive conclusion to German air superiority over Europe and many other war theatres, played as important a part in the latter years of the war as the Spitfire did during the early years of the war.