Originally Posted by
cmgalan
I think you still have to be E75 or SE100 to upgrade in ACV even if you are in a Flex fare. Hopefully, for your sake, I'm wrong.
ACV will generally not book into Flex for economy. But the rule of thumb is to only use them if there is a price advantage for a Y or J fare (often will be for sun destinations) over ac.com, or if you're bundling your hotel with the trip.
Otherwise book directly from aircanada.com