Airlines oversell their flights due to the number of no-show passengers from a variety of reasons including missed connections, arriving late, having too many drinks in the airport lounge etc.

Airlines have been changing their oversold procedures after the recent incident where a United Airlines Passenger Was Dragged Off Plane Due To Oversell, and with the recent changes for instance, Delta is allowed to offer up to $9,500 in compensation and United can offer up to $10,000.

Delta has led the way when it comes to soliciting volunteers for oversold flights, as passengers are prompted at check-in both via the website and the kiosks, notifying them their flight is oversold and asking if they are interested in taking a later flight in exchange for compensation.