Just noticed in another thread you were deciding on a FF program. Note that if you pick AA then the BA miles across the pond do not count.
However, if you are traveling trans-Atlantic after July 1 you can take BA LHR-YYZ and then AA YYZ-ORD(or MIA)-ATL and get mileage credit for the BA flight.
Keep in mind the two stopover rule in NA and the 20 segment maximum rule when doing your planning.