I just purchased Finnair economy found on Google flights linked through to AA that had an AA codeshare inbound and BA codeshare outbound, not sure why but was much cheaper than searching directly on AY, BA, or AA.

Even though I purchased a Main Cabin (not basic) Economy ticket, I had no option to select my seat on AA or through the Finnair website or Finnair app using either the AA or AY confirmation (the AY confirmation is the only one that works anywhere else). Thanks to this thread, I tried RJ and RAM with both my AA and BA numbers attached separately, and neither let me choose a seat.

I did the chatbot and the agent said it would be 45EUR for each leg to select my seat early. So I guess that or rolling the dice on check-in is really the only option (not a big deal, currently only 5 seats booked on the whole flight ha ha).

I tried the AY Upgrade page but it says no biz seats available right now (flight is June). Says you have to call for PE upgrades. Not sure when these are normally released.

Has anyone been able to upgrade to either Premium Economy or Business on AY metal when on an AA or BA codeshare?