The U.S. Department of Transportation fined American Airlines a record $4.1 million for violating statutes on tarmac delays of three hours or more on domestic flights without providing passengers an opportunity to deplane. DOT’s investigation found that American kept dozens of flights stuck on the tarmac for long periods of time without letting passengers off.

An extensive investigation by the department’s Office of Aviation Consumer Protection (OACP) found that between 2018 and 2021, American allowed 43 domestic flights to remain on the tarmac for lengthy periods without providing passengers an opportunity to deplane in violation of the department’s tarmac delay rule.

DOT said none of the exceptions to the tarmac delay rule, including the safety and security exceptions, applied to the affected flights. In addition, on one of the 43 flights, passengers were not provided with food and water as required. Most of the delays occurred at Dallas Fort Worth International Airport. The tarmac delays affected a total of 5,821 passengers.

The $4.1 million fine is the largest civil penalty that the department has ever assessed for violating the DOT’s tarmac delay rule. Of the $4.1 million assessed, $2.05 million will be credited to the airline for compensation provided to passengers on the affected flights. DOT encourages airlines to compensate passengers by providing these credits so that a portion of the civil penalties that would have been paid to the Federal Treasury is instead used to compensate the affected passengers.

Pete Buttigieg, transportation secretary, said this is the latest action in a continued drive to enforce the rights of airline passengers. Whether the issue is extreme tarmac delays or problems getting refunds, he said, “DOT will continue to protect consumers and hold airlines accountable.”