The Transportation Department fined Delta Air Lines $750,000 on Wednesday for bumping passengers from full flights without asking for volunteers and without detailing compensation available.
Delta had similar violations in July 2009, when the airline was fined $375,000.
"Airline passengers deserve to be treated fairly, especially if they are forced to miss a flight because an airline oversold seats," Transportation Secretary Ray LaHood said in announcing the fine. "Consumers have rights, and we will continue to take enforcement action when airlines violate our rules to protect the traveling public."
Federal regulations require airlines to seek volunteers willing to give up their seats when flights are oversold. If passengers still need to be bumped, they are entitled to up to $1,300, depending on the cost of their tickets and length of delay.