Originally Posted by
greggariouspdx
Thanks for the feedback on this topic. I actually spoke with a very helpful Air Canada Agent (yes they do still exist) and he explained that as long as I am going from USA to International and vice versa, that I do not have to deal with Canadian Immigration. He also added that the YVR stopover is out...I must do PDX-YYZ-EZE. Soon I can post my thoughts on AC's executive class.
I'm pretty sure that the "very helpful" Air Canada agent is wrong and you do have to deal with Canadian Customs and Immigration. Even the YYZ website seems to indicate that's the case:
http://torontopearson.com/Connecting_from_usa.aspx#