the airplane's AI is severely crippled in this game. They have limited commands that can be used. Now contrast this with the ships and AI subs - they have a huge command list and you can basically do anything you want with them. It's quite apparent that the airplane's weren't given hardly any attention but they are the most important (in my eyes) in the game.
It's so ridiculous that the airplane has to have either a bomb or torpedo on it in order for it to attack you with it and cannons. Once that bomb or torpedo has been fired it goes back to following waypoints even though it has cannon ammo left. The devs made it this way because it's too stupid to know that you submerged and it can't see you anymore (it still thinks it sees you even though you are 40+ meters down
). So airplanes that only have cannon ammo just fly right by you and don't even come to investigate or take a shot at you. Like I mentioned before I can make them come and investigate and shoot at you with those cannons but then it's a suicide mission for them - they will eventually run out of fuel and crash
The lucky ones will run out of cannon ammo and then return to following waypoints.