Unfortunately, they forgot to mention it to the US government.

Or perhaps it was the fact-checker’s day off.  From a recent New Yorker profile of film maker James Cameron:

I first met Cameron in April of 2008. “Avatar” was in its third year of production. For much of that time, Cameron had been working out of a couple of hangars in Playa del Rey, south of Los Angeles, where Hughes Aircraft manufactured fighter jets during the Second World War.

via James Cameron and “Avatar” : The New Yorker.

There were a few jet fighters operational late in the war, in particular the Messerschmitt Me 262, but Hughes wasn’t building them.