I currently have a package called Ultimate Traffic which provides AI aircraft and routes for all airlines around the world.
I have recently downloaded several upgrades to airports (London Heathrow and City) which appear to have their own AI aircraft, which are not very good quality compared to Ultimate Traffic.
Is it possible to remove the AI aircraft without removing the whole airport upgrade, therefore allowing my original Ultimate Traffic package to provide the aircraft? Will this also involve removing any arrival / departure schedules also written into these upgrades?
As you can tell, I am still not at the stage of knowing exactly what files do what, and where they are located!!
Check this out. I hope it does what you want.