I’ve got a method that I’ve been using for a while to prevent these types of spawns. Although it has removed a lot of the ambient spawns, such as vehicles pulling in/out of parking lots and driveways, as they share the same system.
I’m working on a new version of this solution to only affect the planes and keep the airport space void of random traffic, and might be releasing it as a resource if it all goes fine.
Edit: The release is available here: [Release] Remove AI planes, cars and spawns from airports