In my opinion not the planes itself are the “problem“. It’s the system and the – exaggerated said - legal abuse of its current mechanisms which are originally not made for IFA stuff and that’s why they’re unbalanced.
Planes are a big advantage in a well-played team match. But they are also the best way just for farming kills without any need of teamplay. Their cost-benefit ratio is nearly ridiculous high and it’s the best of all vehicles if not to say of all weapons. They are cheap, have huge firepower, are hard to destroy or even just to hit for normal players and a good pilot could gain an extreme high amount of XP and money in a short period of time. I think that’s the main reason why some players do nothing else than flying and bombing and circling over the AO and the spawns to get cheap and easy kills (some of them don’t care about the team and switch side if they lose air superiority, but that’s another topic). The result is plane spam.
I believe a combination of adjustments would be more effective in reducing the plane spamming and make them less attractive for killfarmers without losing their advantages for teamplay. So here are my suggestions.
First of all make planes more expensive. Pilots should “feel” their loss if they got destroyed.
Second one is to raise the time period to get another plane after losing one.
And as the third adjustment the money and XP earned by kills with a plane should be reduction. A reduction of the endgame bonus would be also possible but I don’t know how many work this needs.
All three points in a balanced combination could reduce the current problems with planes.
I hope my english wasn’t too bad ^^