5. Being too fat
It’s sad (and embarrassing) but true: if you can’t show the flight attendants that your armrest will go down and stay down, you may not be allowed to fly. An American woman died stranded in Hungary in 2012 after being denied a seat aboard three separate planes due to her size, and director Kevin Smith was removed from a flight for being overweight in 2010. Some airlines (cough, Samoa Air, cough) actually calculate your airfare by the pound; as the cost runs between 44 and 48 cents per pound, you might want to think twice about cronutting (yes, we're already making it a verb) prior to check-in.