I've traveled to US several times and never been asked for a BTA, n fact not sure what it is! A quick google and it could be...
British Triathlon Association
British Tinnitus Association
British Trout Association
British Thyroid Association
or the best one
British Toilet Assoication
None of them sound very likely in this context though
pls can u explain yourself more clearly bbeverle@ya ?
who is the "they" that ask for a BTA [British ??] and what is it. and where do you get it, does it cost money ? because I fly to US quite frequently and I am baffled.