Originally Posted by nufnuf77

I have had my fair share of problems with AA online check-in when international journey and codeshares are involved. If you can't check in with BA at T5 I recommend heading over to T3 AA counter before departing for OTP, as that will be your ultimate last chance. Notice the check in will close before you land at OTP so HBO/Airside/Landside won't matter, you need to be checked in by deadline 1h before OTP-LHR-PHX...