When I used to use film and back in the late 80’s when we had flights between Galway & London going out at 6.50am & returming at 9.40pm I used to travel a bit to London to do weddings. I always took the films through the hand luggage section. I then got a lead-lined bag to carry them in. Never had a problem ………. but I do know that if they went through the luggage section they were in danger of being fogged. One other thing I did was, I always shot these weddings on 35mm so that the film was inside a metal container and was being shielded by the containet also.