I was on a BA flight recently (LHR-JFK) and I was given a sealed cheese and tomato sandwich by a flight attendant about 90 minutes before landing. Everyone else was given a similar sandwich, probably as an afternoon snack. Because I was not hungry I kept the unopened sandwich on the empty seat next to me knowing that I would probably be hungry after immigration queues etc and I would eat it on the car ride into the city.
Just before the plane began its approach to JFK and the flight attendants were doing their last safety checks before landing, the same flight attendant told that I would be unable to take the sandwich from the plane and I would either have to eat it before disembarking or throw it into the bin! Not being hungry I left the sandwich behind.
Why can't I take food off the plane? Is this a USA thing or an international thing?