Yeah, as you mention, Phantom Air Mission is indeed the same game as Flight Of The Intruder I dont know why they released the game with two different names. Maybe due to some copyright issues that were only present in Europe and/or in the US?
EDIT: I forgot to mention, i think that i had been collecting NES games for a few years before i first heard of Phantom Air Mission myself. So it is kinda the same with me when it comes to knowing about Phantom Air Mission, i also didnt know about that this game existed to begin with