The DOT becomes involved when not enough passengers volunteer and some travelers must be involuntarily bumped. The amount depends on the price of their ticket and the length of the delay. Passengers involuntarily bumped may keep their original tickets, which they can use at a future date or have refunded.
Rules differ for international flights and for flights overseas.
C-75 Room 4107, Washington DC 20590. Or, you can visit the consumer information section at the DOT's Web site . Airlines are required to make all best efforts to fly you to your destination in the timeliest manner possible. If the delay between the flight from which you were bumped and the replacement flight is less than one hour, no compensation is offered. This amount is doubled when the substitute flight delay is greater than two hours or if substitute travel arrangements have not been made, which may not always be possible.