Does completing a location stop vehicles spawning?

Solution 1:

Yes, the planes will keep taking off while the location has not been completed, but once you complete it, they stop.

This is actually an issue with the game that can prevent 100% completion. There is at least one jet type that can only spawn in the "taking off" mode, so if you inadvertently complete all the locations where it can spawn without hijacking that jet type, you will never have another opportunity.

Solution 2:

It's true that jets keep departing as the base is still not taken over, but that's not the point here.

There are infinite jets no matter how many bases you take over (I know this cause I did took them all over), because jets will still spawn in the hangers, these hangers are usually located next to a runway so you can take off easily. Also they will still randomly spawn flying trough the air every once in a while (though they are very hard to catch).

Basically the only thing you are stopping from happening are the jets that take off every time you visit a base/airport. You will still be able to find lot's of them, don't worry.