Stealth
My understanding of this issue is that that the airport operators do not want bods in uniforms on their patch, presumably from a security standpoint. I believe it has been agreed at MOD level. The theatre commanders (whichever one you may be in) have been told that part of the return brief is to have a set of civvies to change into if you are moving onward through a civil airport (not that the suntans and nice green sandy luggage wont give the game away).