Originally Posted by
hgwatts
I've done this quite frequently by having the agent (either ticket counter or gate) put my FF number in when I'm at the airport. I've never had trouble, but always kept my boarding passes and made sure the miles posted.
It very much depends on the programs involved. The OP is talking about AC and BA so I don't know the specifics there, but I do know that on DL they can't/won't change the number in the record once travel has started.