Originally Posted by
GRUflyer
I do that all the time, by using Avios to book IB/BA and then claiming I will book for someone else and enter my AA FF# at time of booking or later. No issues at all, and F class lounge access at LHR and priority in ordering meal choices with IB long-haul.
Edit: Since you will be flying AA, the limitation might come from their end, not the booking process with BA. I find it highly unlikely, though.