Question on country definitions

Does anybody know how to change the country definition of an installed aircraft ? I have a couple of US aircraft I recently installed showing up under the British flag...I'd prefer to keep things proper. If it makes any difference I havent bothered with the Nationalities expansion pack yet...thought I'd wait till more aircraft of different nationalities become available first. Apologies to all the Commonwealth nations...and Hungary. Is there a quick fix for my problem ? I'm hoping its just a simple case of changing some text line...problem is finding the right one. Any help is appreciated.