Originally Posted by
serfty
Only using AA.com - on AAwards I do book like this.
I replace the AA number with my QF number in the appropriate input field
That has two downsides:
1) AA FF number isn't in the booking any more, so it won't list under your bookings on aa.com.
2) AA.com made a change to remove all your pre-filled details if you remove the AA number, which means having to enter them all again.