Originally Posted by
CloudCoder
Definitely a case of HUCA. (Or perhaps LOTA Log Off Tweet Again,

). You can display the record on BA.com, AA.com, or whereever it is, and you can change the FFN to you CK number, AS number, AA number, etc, i.e. any number of your own choosing, or you can blank it out entirely if you wish.
If it were me, I'd go to AA.com and find the reservation by Flight # and Passenger Name, then change the FFN.
This would work to ADD a FFN (if there isn't one at all in the record currently), but definitely for AA.com, once a FFN is in the record, you can't change it yourself online. Don't know if the Finnair avenue still works as there seem to have been mixed reports on that.