One more thought Triley. As you know, the Delta code is only valid for domestic travel. So you would have to book 2 separate tickets, for example, BOS-YYZ/YUL-BOS, and YYZ/YUL-YHZ-YYZ/YUL. Surely that will end up being more expensive than BOS-YHZ-BOS (even if it's routed through YYZ or YUL) even with a 15% discount on the domestic ticket.