Several years ago when the airlines began enhancing their identity-checking procedures for passengers to make sure the person flying was the person named on the ticket, they began asking people to present the credit card that they used when they purchased the ticket along with the ubiquitous "gov't issued photo id card". Why do they do this? Does it have something to do with credit card fraud? What happens if you don't have the card on you when you go to the airport? Sometimes I cancel a card, or I leave all but one or two at home to avoid loss or theft, etc. What if I leave "The Card" at home?