(from the AC Maple Leaf lounge in YVR)

My inbound flight from SEA was late, so I missed my connection to YYZ. Since I now had a long layover, I decided to look into the transit issue by talking to AC. They told me exactly the same thing that Ken Hamer already stated - you do NOT need a visitor visa to transit thru YVR.

Even when I was coming in - I noticed that the pathways diverged - one pathway had a sign "Canada arrivals - Customs" leading downward into the immigration / baggage / customs area while the other pathways went upstairs and the sign said "US and International Connections" - so unless you wander into the wrong area you will not need a visitor's visa.

So it doesn't matter whether you are flying AC or CP or any other airline - the procedure is the same.