BA seems to be gracious in this area. I've had the priviledge of landing in SFO, LHR, and NRT several times in the last year. All on 747-400's. I've also had the extremely good fortune to be up front during takeoff from LHR and NRT a few times. I've always asked the FA while settling in upstairs and provided some form of ID. It's worked a fair amount of the time, but it always comes down the the flight crew. I've enjoyed every opportunity!