Originally Posted by
happychic
I just tried it again on Finnair's website. I had to click on the "Change" button to add my FF number. Idk why I didn't see it before LOL. Thank you y'all! One less thing for me to worry about planning my travel day logistics

Check it again in a couple of days to make sure it has stuck. There are some accounts of it ending up back at the AA number which might be problematic if you are trying to use your BA One World status to access lounges beyond your AA status.