Originally Posted by
Buster CT1K
I have an AA ticket (bought with cash) on BA 777 J. The route is JFK-LHR and LHR-JFK. I would like to upgrade to F on day of departure. Is this possible?
Yes. You can ask at check in with BA if there is an AUP (airport upgrade) available. See:
Airport Upgrades (AUP) promotion 2021/22 thread