Originally Posted by
CanuckFlyer
However when I try to use it to get from YYZ to SFO, only Tango Plus fares show up. If I try YYZ to YVR, I get Tango and Tango Plus.
Tango fares are only offered within Canada and (now) to some Asian destinations. It's a way for AC to compete on a Apples-to-Apples basis with other carriers that don't offer Alliance miles as an incentive (WJ, Porter, Hainan, etc.)
Since most of its transborder competitors offer 100% mileage accrual on even the cheapest fares, there isn't a market for Tango fares in there.