 The first production contract was awarded by the British for 320 NA-73 fighters, named Mustang Mk I by an anonymous member of the British Purchasing Commission; a second British contract soon followed, which called for 300 more (NA-83) Mustang Mk I fighters.Contractual arrangements were also made for two aircraft from the first order to be delivered to the USAAC for evaluation; these two airframes, 41-038 and 41-039 respectively, were designated XP-51.The first RAF Mustang Mk Is were delivered to 26 Squadron at RAF Gatwick in February 1942 and made their combat debut on 10 May 1942.