The U.S. Department of Transportation (DOT) announced August 28 that it had fined American Airlines $4.1 million for unlawfully keeping thousands of passengers waiting on tarmacs for hours over a period of three years. This is the largest fine ever handed down to a carrier for violating the DOT’s Tarmac Delay rule, which prohibits airlines from postponing domestic flights for three hours or more without giving passengers an opportunity to deplane.

Half of the $4.1 million will be credited to the airline to provide compensation for passengers impacted by the delays.

American Airlines kept 43 domestic flights on tarmacs for three hours or more without giving passengers an opportunity to get off the plane between 2018 and 2021, according to an investigation by the DOT. The DOT said that these delays affected 5,821 total passengers.

The fine, which is the biggest penalty ever assessed by the DOT for violating the tarmac delay rule, comes as part of the Department's effort to ensure the protection of public travel, which includes returning more than $2.5 billion to travelers in refunds.

“This is the latest action in our continued drive to enforce the rights of airline passengers,” said U.S. Transportation Secretary Pete Buttigieg. “Whether the issue is extreme tarmac delays or problems getting refunds, DOT will continue to protect consumers and hold airlines accountable.”