We have a scenery where we have some nice traffic running around, but we also have some default guys elbowing their way in. How can I git dem 'defaulties' to hit da road, Jack, don'tcha come back no more no more no more....?
If you want to do it permanently - for all airports - then simply delete/disable the default AI traffic file in the Scenery\World\scenery folder (traffic 030528.bgl in FS9, trafficAircraft.bgl in others).
However, if you want to have some default traffic at some airports, then you'll have to get creative and modify the stock traffic file. (Several options in AIFP).