This isn't viable as its too hard to enforce. This is Wasteland, there are no safe zones. If people want safezones they should play Altis Life.
Here is your solution, and believe this is coming from someone who HATES planes/heli's with a passion.
Planes should stay. Why? They are a part of the game. Just like heli's and tanks. When a tank is bombing a gun store.. leave? Go to the airfield and take it? Wasteland is huge. When my area starts getting bombed or mortared, I sit on the edge of the hotzone and wait for the plane to pass and pick off people as they enter. When they enter, planes wont bomb (or shouldn't) a gun store with friendlies in it. Go kill them, return to your spot just outside the hotzone and repeat.