If I were you, I'd rethink taking either BA or AA in First, and would choose RJ in Business. The connections in AMM are excellent (and therefore the overall travel time is considerably shorter) and the RJ service is superb. You'll save lots of $$$ of YQ (fuel fines), some AA miles, and most importantly, loads of potential grief at LHR. To the extent that LHR is avoidable, you should strongly consider avoiding it. Taking BA or AA has you on a 2:35 am flight from AUH, with an unpleasantly lengthy stop at LHR (i.e. from 6:25 am to 11:40 am), whereas RJ leaves AUH at 8:00 am (but arrives in ORD just an hour or so later than either the AA or BA connections). To me, the RJ flight times are vastly superior.