If you go into the folders of the individual aircraft, and find their aircraft.cfg files, you can edit them there.
In the [fltsim.x] section, you can find some headings, including:
These change where they show up in your Aircraft menu in FS
. ui_manufacturer is the highest division (what might be Boeing, Airbus, Bombardier etc...), ui_type would be the aircraft (737, 747, A320 etc...), and ui_variation is usually the paint scheme.
I've changed it such that ui_manufacturer is the airline (American Airlines, British Airways, Continental), ui_type is stillt he aircraft type, and ui_variation is any defining characteristics (whether it's a special paint scheme, a developer, or something like that).
So I might have American Airlines->Boeing 757-200->American POSKY (for Project Open Sky), or American QW
(for Quality Wings).
Works really well for me.