North American P-51 Mustang XP-51

When Mustang production began for Britain — 320 NA-73 fighters on the first contract and 300 NA-83s on the second, all of them Mustang Mk Is for the British Purchasing Commission — contractual arrangements were also made for two aircraft from that first order to be delivered to the US Army Air Corps for evaluation. Colonel Oliver P. Echols arranged the handover with the Anglo-French Purchasing Commission, and the two airframes, serials 41-038 and 41-039, were designated XP-51.

The pair reached Wright Field on 24 August and 16 December 1941 respectively. The small size of that first American order reflected the state of the Air Corps, still a relatively small, underfunded peacetime organisation until its reorganisation into the United States Army Air Forces in late June 1941; priority had to go to building as many P-38s, P-39s and P-40s as possible while training crews, so evaluation of the XP-51 did not begin immediately. That did not mean the aircraft was neglected or the testing mishandled: flying-qualities and stalling trials of the XP-51 produced a dedicated NACA report dated April 1943.

These two airframes should not be confused with the P-51A: the Mustang I (NA-73 and NA-83) and Mustang Ia (NA-91) built for the British were not equivalent to that later model. The material consulted does not detail the specific armament or measured performance of the two XP-51s.