The department said that it had fined six airlines a total of $7 million for failing to give refunds on time. More than $600 million in refunds were issued by the airlines due to the department's intervention.

Frontier Airlines was fined more than any other airline. As a result of Monday's announcement, it was the only U.S. airline that has issued refunds.

The department said the refunds were supposed to compensate passengers for flights that were canceled.

Pete Buttigieg, the transportation secretary, told reporters on a call that the D.O.T. has their back.

The second-largest fine was assessed to Air India, amounting to over one million dollars. Three of the four carriers will pay less than $1 million. The Office of Aviation Consumer Protection has issued a record $8.1 million in fines over the course of the next four years.

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Frontier said it had issued about $100 million in refunds that were not required. The DOT credited the airline for giving refunds to passengers who canceled non-refundable tickets early in the P.H. epidemic.

Travelers have been complaining about flight delays and other problems. After two years of the Pandemic, more people are shifting their spending from goods to travel and other services. People have been so eager to travel that they have been willing to pay more for tickets.

In the past few months, the Transportation Security Administration has screened an average of more than two million people a day at airport checkpoint, or about 95 percent as many as it screened during the same period in 2019.

The fines announced on Monday are part of a continued effort by the transportation department to hold the industry to account The dashboard was created to encourage airlines to provide free hotel stays and meals when travel is disrupted. The department has proposed new rules for how airlines and travel-search websites inform the public of their fees.

The rule that would define when airlines would issue refunds was proposed in August. Most companies give refunds when they are due, according to the airline industry.

The proposal was embraced by consumer groups, but they also complained that the department had acted too slowly, allowing airlines to not refunds customers' money early in the Pandemic.

Some analysts reacted to Monday's news the same way.

The latest round of enforcement from the U.S. D.O.T. is too late and leaves out the worst offenders. The nation's largest airlines should be punished over other mistakes, such as this summer's operational meltdowns.

Mr. Buttigieg said that some of the customer complaints addressed by the fines were related to travel.

He said that they are moving quickly to make sure airlines understand that they are accountable for the rules and for treating customers the way they say they will.

The department has open refunds that are not directed at U.S. carriers. Mr. Buttigieg asked staff to look into whether the penalties were enough to prevent such behavior in the future because the department was more focused on ensuring refunds were paid than on collecting fines.

He said that it shouldn't be happening in the first place. We will keep ramping up the penalty side until we see less of this type of behavior.

The department said that the fines had not yet been paid, but that affected passengers should have been notified that they could get refunds.