I spoke with reps from a major aircraft manufacturer the other day when I was a t their plant for "other" business. Anyways, the people I spoke with were aware of the issue that you are speaking about, and I asked the question you are asking now. Doesn't the US Gov't own the rights to the P-38 P-51 etc names and they replied that I was indeed correct, but as soon as you either enter into contract recognizing that the the above anacronyms are assoicated witha major manufacturer's product line then you have agreeed that it requires licensing. The same goes forth in that if you use North American, Lockheed, or Grumman in the gaming or kit process, then those companys have a right to have their names recognised.
So simply put, drop using the corporate monnikers and if you have no prior licensing contracts, you are set to go.