Originally Posted by CXYYZ
If you decide to go with AAdvantage and fly BA transatlantic, consider BA to YYZ and then connect on AA to your destination. BA flights to/from Canada and Mexico are eligible to earn AA miles, subject to the normal rules.
Or if you choose AA then you also have BA LHR-YVR connecting to Alaska (AA non-OW Partner) for US West Coast destinations of LAX, SFO, and SEA.