What surprises me is the head count. All airlines is supposed to have a head count of all pax on board. It may not be a physical head count but Basically they should know how many on board. I feel why they are fighting hard is not because of your son's issue but a more serious issue of the regulators going after them for having an unaccounted pax on board and flying. If they can prove he did not fly then they get off but if you prove he flew that is a serious issue for AC.