Well, the good news is that almost nothing ever actually departs JFK on time in the evening, so your 1 hour and 26 minutes is likely to grow unless your inbound flight gets delayed. Is it the last JFK-LHR of the night? What cabin are you flying in on the inbound (as that will definitely determine how quickly you're able to deplane)? Also BA will depart from T7, AA will arrive at T8 so it shouldn't be too long of a terminal transfer even though you have to exit the sterile area. Unfortunately BA is still not a TSA Pre✓ participant, so you will have to clear through regular security.