Add two more runways, without hangars or buildings and have the planes spawn in randomly among the three. If a blue plane is on runway "A", no other blue plane will spawn in on that runway until clear. BTB hangars remain at the "main" base, and total distance from runway to enemy hangar is maintained.

not a bad idea...but I don't think that's the exact solution...but its along the right lines I think
one issue with that idea....those guys who just sit on the runway.....or those who are not flying and land there to rest...what if you get three of them?
maybe if we couldn't crash into our blue teammates at all?

My thought was that if you had a "parker" that would automatically send you to a different runway. Also, if you were sitting there with brakes on and hearing the pings of bullets from a spawner, your buddies would respawn away and be able to assist in breaking the hold.

If I was in a game with three "parkers' I would quit so fast there would be an audible pop as the air closed in on where I used to be occupying the space, one parker is enough to make me crazy.