Originally Posted by
FrancisA
Perhaps someone with more knowledge or experience can confirm that this actually works.
I don't think it does.
It's not even 100% reliable if you ask to change FF# at check-in, I recently flew on BA metal (BA code, albeit an IB ticket), at check-in I asked to switch to my AAdvantage FF# instead of my BAEC FF#.
My BP clearly shows my AAdvantage number. Avios and TPs posted anyway.