Why Do Planes Become Overbooked?

Using historical references, forecast modeling, and basic statistical probabilities, airlines know that not every passenger who purchases a ticket will actually show up for his or her flight. So in a quest to fly full planes, and maximize profits on every flight, airlines regularly overbook, sometimes by as much as 50 percent. Airlines have been doing this for years -- it’s not illegal, and normally there are no problems. Usually, there are enough passengers willing to take a later flight, and get financial compensation for the inconvenience. The type of ugly scene that recently played out on United Express Flight 3411 at Chicago O’Hare International Airport doesn’t happen very often.

Now boarding at Gate 12:

• Department of Transportation rules require airlines to seek out people who are willing to give up their seats for compensation before bumping anyone involuntarily.
• Each airline has “boarding priorities” when a flight is oversold. When there aren’t enough volunteers, some airlines will select the passengers who paid the lowest fares to be "bumped" from the flight. Others bump the last passengers to check in.
• On average, about 1.3 passengers out of 10,000 are denied seats against their wishes. For every person bumped involuntarily, there are about nine passengers who volunteer to be bumped.