Originally Posted by
finiteyoda
I guess I had good timing, I knew there was a good reason their website was down so long last night!

Few more questions regarding the chart (sorry, I'm still completely new to deciphering these...) Is the chart for one-way or round-trip? Also, where they show fare class, is that to upgrade "from" that class to ExecFirst? Why would you upgrade from C/D, I thought AC doesn't have a true F product? And why would upgrading from Y/B use less points than upgrading from C/D?
Finally, for a given flight, how do I know what fare class it's in? Are all Tango Plus fares considered Y/B, and eligible for the upgrade?
No Tango Plus fares are considered Y/B, Y/B fares are Latitude.
The mileage chart is not just for Air Canada, it is for AC redemptions on Star Alliance too. If you were to purchase an AC Latitude fare, you could use either your AC or UA miles to upgrade (subject to availability). The reason that you can upgrade from C/D is that you can use your AC miles to upgrade from Business to First on those participating *A airlines that have both Business and First classes.