Resurrect this thread on using partner FFP number for Mileage Plan booking.

I know some people created a second profile with partner FFP number for revenue booking. Does using this second profile in mileage plan booking retain the partner FFP number or it would error out?

Alternatively, have an alternative profile without any FFP attached. Then try to add the partner FFP number from partner’s end? In this case the partner is AA. The passenger has AA Gold so will get one free checked bag and selection of preferred seat, versus no status at AS. Hence the incentive to change to AA number.

on top of that AS is 7.5K vs AA 12.5K, that is the reason to use AS program.

Update -
The "Alternate" profile without AS number worked. AA website showed the FFP box in white versus grayed out. The AA number added was successfully saved luckily. No need to use chat / twitter. Ressie shows up in AA account with corresponding benefits.