The question that I have is how did Lt. Roddenberry get his hands on a United States P-38 Lighting? I would have thought that a semi-obsolesent aircraft for the time period wouldn't have been sold or borrowed to someone from another nation since it could have been used against them (the USA) at some point in the future. They are a semi tyrannical government after all.
Remember that circa 1939, Lockheed sunk some 6 million dollars of their own private money into the development of Kelly Johnson's then far-out design before the first governmental XP-38 and YP38 orders. And if Kekky Johnson and/or some of the other Lockheed engineers and designers had chosen to flee the unpleasantness in Burbank prior to the founding of the Lockheed *Skunk Works* in 1943, the following Lockheed aircraft designs more probably would have taken place wherever they relocated and set up business- The formal contract for the XP-80 did not arrive at Lockheed until October 16, 1943.
An awful lot of the US WWII aircraft development took place in California, and the emergence of the Northrop and Horton design *Flying Wings* suggests that in the RT world, some designs that were less successful in our place and time that were abandoned were better developed in the RT existance.