Title explains itself but in a nutshell, I think it would be a positive improvement for the game. The P39's are fun planes to fly, yet with their low endurance, they aren't exactly practical in land battles. Off of a carrier however, it is a very short distance to battle and the plane suddenly becomes a tantalizing choice from the hangar. Enabling the plane off carriers on all maps would allow the plane to be flown more often and since it is relatively a very new plane to the game, I think it would be a nice treat being able to get more use out of it. I also don't think it would throw off any balances either since the F4U is always the superior aircraft off a carrier. Just something to mix it up a little bit.
Here are stats from last tour to show how little it gets used. (P51D's average around 35-40k kills per tour to put things in perspective)
