Train Guard: Sorry sir but you can't board the train without your tickets.
Father: I must have lost them on the tube.
Train Guard: Well if you tried to board a plane with no ticket, they wouldn't let you on would they?
Father: Well,
yes they would because they'd have your e-ticket and passport information.
Train Guard: =O
-A while later-
Son: Wow Dad that was such a
Nerd Bomb.