The Department of Transportation announced it is fining American Airlines over $4 million for keeping thousands of passengers on the tarmac for an unlawful amount of time. The $4.1 million is the largest ever penalty for violating the department’s tarmac delay rule. Of that fine, $2.05 million will be credited to American Airlines for compensation provided to passengers of impacted flights.

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

According to the department, American Airlines allowed 43 flights to remain on the tarmac for lengthy periods without providing passengers an opportunity to deplane. On one of the 43 flights, passengers were not provided with food and water as required.

The tarmac delays affected a total of 5,821 passengers. Most delays occurred at Dallas Fort Worth Airport, according to the department.

American Airlines told the department the tarmac delays were the result of exceptional weather events, and that they represented less than 0.001% of the approximately 7.7 million flights operated by American and its regional partners from 2018 to 2021. The airline said it has committed “substantial time and resources to improve its performance on tarmac delays.”

“We have since apologized to the impacted customers and regret any inconvenience caused,” the airline said Monday. “American respectfully disagrees that certain of these tarmac delays warrant enforcement action under the extreme circumstances presented.”

Monday’s fine came seven years after the department fined American Airlines a then record-matching $1.6 million after it found the airline had allowed flights to stay on the tarmac without allowing passengers off the plane. The department is also investigating Delta Air Lines for a similar incident in July of 2023.

At least one Delta passenger was taken to a Las Vegas hospital for heat-related illness after the plane sat on the tarmac for hours. Buttigieg described the incident as “infuriating” and “shocking.”

“I want to know how it was possible for passengers to be left in triple-digit heat onboard an aircraft for that long,” Buttigieg told Reuters in July. “Even under normal temperatures a tarmac delay is not supposed to go that long and we have rules about that, which we are actively enforcing.”