I am playing on a Flans Server with friends and while playing we noticed that rocket launchers of any kind are way too strong against any aircraft. The issue we're having is not really the damage of the launcher but more the speed of the projectile.
A plane can be 300 Blocks above the infantry soldier on the ground but that doesn't put the plane in a "safe spot" at all. The infantry soldier on the ground can still easily instant kill the plane. That isn't just (in my opinion) rather overpowered but also makes any kind of anti aircraft gun nearly fully obsolete since they turn slower and are stationery etc. which makes them in comparison an easy target.

Solution:

My solution to the problem would be rather simple though. Like I already sort of mentioned do I see the problem in the lightning fast speed of the rocket. So what I would do is alter the speeds of the rockets so that they're not that fast so when planes fly high enough it's pretty hard to shoot them down with a rocket launcher. And if that's not something you agree with than at least give the player the possibility to change the speed of the rocket in the config since that would make everyone capable of altering the speeds according to their "believes" and needs.

(If it is possible to change the speeds of rockets than let me know how because I couldn't find any option to do that in the config)

Appreciate your work and thanks for reading my suggestion.