Originally Posted by
WineCountryUA
understand on the AC online limitation but in the past PMUA you could call -- multiple AC agents have told me that is no longer true for the new UA (as it was also not possible for PMCO).
You can definitely call AC to get seats assigned when on a UA ticket -- I just did it yesterday. The seats aren't shown in the original UA reservation but are listed when you view the reservation on AC's website.
On its lowest ("Tango") fares in North America, AC doesn't allow advance seat selection to anyone, regardless of booking channel, without a fee. So perhaps this is why you ran into problems.
Most AC fares between Canada and the US are at the "Tango Plus" level which allow advance seat selection, but some of the more "leisure"-type destinations do have the Tango fares. (Note also that Tango fares in North America earn 0 Mileage Plus miles, so you really want to avoid them).
Warning: I generally find that I have to wait about 30-45 minutes on hold before I get to speak to an AC agent. Very frustrating when all you need is seat selection.