What would the United States do in 1939 with two XF5U prototypes fitted with Harrier-type engines?
Short answerDismantle one to study the engines and test the other for performance data, using them as technology demonstrators rather than immediate production aircraft.
NotesFitting Harrier-type engines would make the aircraft something other than a normal XF5U, but the United States would still exploit both prototypes. One would likely be dismantled so engineers could study and reverse-engineer the propulsion system. The other could remain intact for flight testing and performance measurements, taking advantage of the XF5U family's unusually low stall speed and experimental planform. The counterfactual illustrates that receiving future hardware does not supply the factories, materials, or engineering knowledge needed for instant mass production.