Originally Posted by
flying_tech
Not seen that issue before. Usually it fails to book because it can't find one of the flights not that you find the flights and then it fails. Is there a hidden message somewhere on the screen telling you the actual issue?
BTW - make sure you use your BA executive club number in the booking not the AA one and change the dropdown to BA executive club on Passenger details.
I've booked a multi-city AA flight on their UK portal so I know it's possible...