What is the AA forum's combined experience with this?
Shall I better change proactively already or may I slip through?
Thanks for advise
P.S,: To add, yes we have checked bags, but this is a US-Europe and bags are checked through with no need to pick them up in JFK.
If you are below MCT then the computers will keep catching it and auto rebooking you. There are lots of LAX-JFK and JFK-LHR flights, I would for sure do your homework then call AA back and ask to switch to something else. If you want to stay on the same BA JFK-LHR flight, then just ask for an earlier LAX-JFK flight.