Originally Posted by
bennos
However, as YVR is a preclearance airport immigration is handled before leaving Canada and any bag will be checked through to the final destination without claiming and rechecking in the US.
On the return... yes. No such luck on the outbound.
I would also add that even for the return, AA probably has a dozen flights per day out of YVR where AC has a dozen to YYC, a dozen to YYZ and 4 or 6 to YUL.
It also assumes OP has an ESTA or whatever visas required to transit through the US.