I'll take a shot at this since I'm bored... Have occupancy be based on physical occupancy with a time limit based on a reasonable value corresponding to expect

I'll take a shot at this since I'm bored... Have occupancy be based on physical occupancy with a time limit based on a reasonable value corresponding to expected airspeed for the location. Of course airports would still control the landing/takeoff order because that's what they do. I suspect the FAA has rules against blimps and helicopters hanging out in the paths the jumbojets take so I don't really see any way it would be possible to squat in a particular piece of sky. For smaller drones, I really doubt there will ever be more drones flying around than birds and they seem quite able to share the airspace with a minimum of problems aside from becoming lunch for malicious actors or colliding with ground based vehicles.