If the P36 evolved into the P40 Warhawk, where does the P38 Lightning come in?
If you are concerned about the jump in ‘P’ numbers from one to an essentially evolved version of the same basic aircraft don’t be. The ‘P’ identified (P = pursuit) was allocated by the Air Force when they issued a specification or even an outline requirement to a particular aircraft company or were about to adopt the type into service. Prior to that the aircraft would often be referred to by the maker’s model number, in the case of the P36, as the Curtiss Hawk Model 75, or in some cases simply by a draft specification number other than a ‘P’ number. So, the small batch of North American NA-64s, outdated in concept and deficient in performance, en-route to delivery to the Thai Air Force, was siezed and returned for service in the U.S. when war started. The plane was belatedly allocated the next designator available, P64. By that time the much superior, even in its undeveloped form, NA-73, had already been rechristened the P51. The P36 and P40 (Curtiss Hawk Model 81A) were Curtiss produc
