Originally Posted by
emcampbe
There's very few cases when AC will allow you to select seats online if not booked on Air Canada's web site. That includes, at least until fairly recently, not sure if it's till the case, Aeroplan award tickets. So unfortunately, this will likely require a call to AC. This was supposed to be fixed a couple of years ago, but as I understand it, still isn't.
We weren't able to reserve our seats as a UA codeshare in July. We tried the long phone call but no help there either. Its worth a shot but I wouldn't bet on it