Ambassador, British Airways; FlyerTalk Posting Legend
Join Date: Apr 2012
Location: Leeds, UK
Programs: BA GGL/CCR, GfL, HH Diamond
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If you go via a TA you can only use the GUF at the time of making the booking with the TA, and cannot apply it later to an existing booking. If you book with BA directly you can apply the GUF at a later date but you do this with BA, you can't use a TA to GUF an existing booking whether it was made with BA or a TA.