This is a nifty little trick I learned on FlyerTalk in this thread. Hat-tip goes to turkeyRIOO for showing me how to change the frequent flier number in my Avios booked award ticket from LAX to OGG on AA. When I booked it a few months ago, I didn’t really care which frequent flier number showed up as I don’t have elite status on any airlines. I was able to book seats on AA.com and that was enough.
Just a couple weeks ago, I got a Citi AAdvantage Amex which comes with nice little benefits like priority boarding and one free bag for me and also for my husband who is booked on the same PNR but to access the benefits, you must have your AAdvantage number in the booking. I was able to pull it up on AA using “Find A Reservation” but the frequent flier field had my BA number in it and it was greyed out so I couldn’t change it.
I could have called AA to change it but with no elite status, I usually end up on hold for 30-40 minutes, but the Finnair trick worked like a charm. The details are in the FlyerTalk thread referenced by turkeyRIOO.
It’s quite simple, just go to Finnair.com, enter your name and BA record locator. You will see a link to update your details. Click on this, enter your AAdvantage number and done! Then go back to AA.com and you should see you Advantage number in your profile under the reservation.