Originally Posted by
MelP
I booked a trip on AC for Labor Day weekend and want to add my UA Mileage Plus number - when I do it online and hit Submit I keep getting an error. Had no problem adding my TTN to the reservation. . Anyone else have this problem? It's an Economy Standard (G class) fare. If this persists, would I be able to add it at the airport? Don't fly AC or UA much and it's a short trip but miles is miles.

yes, I had this issue. Adding it to anyone in my Aeroplan profile didn’t work. Also, adding it for my kids on a new reservation (after it failed to be added in their profile) wouldn’t work…I entered it and didn’t show an error or anything, but just didn’t show up at all after booking (nothing indicating anything was wrong - just noticed the info didn’t show up under kids names like it did for mine and my wife). Incidentally, adding it while booking for my wife did work, even though it wouldn’t work for the kids.
I was able to eventually get the kids numbers added to the reservation by calling. I was then also able to add it their profile properly (for next time, I guess) by adding it in the app. Website doesn’t seem to accept it.