A Senate subcommittee on Tuesday slammed U.S. airlines large and small over fees to pick seats on flights.

Between 2018 and 2023 American, Delta, United, Spirit and Frontier brought in $12.4 billion in seating fees, including for seats with extra legroom as well as those in “preferred” locations that are closer to the front of the plane, or window or aisle seats, said the report from the Senate Permanent Subcommittee on Investigations.

Last year, United’s revenue from seating fees totaled $1.3 billion, the first time since at least 2018 that category surpassed checked bag-fee revenue, the report said.

While most major U.S. airlines have gotten rid of ticket change fees for standard economy tickets, they have added fees to select more popular or roomier seats on board. Carriers have also been racing to add more premium seats on board to increase revenue.

Stamping out so-called junk fees has been a priority for the Biden administration. Sen. Richard Blumenthal, D-Conn., the subcommittee’s chair, said airline executives have been called to testify about the practice at a Dec. 4 hearing called “The Sky’s the Limit—New Revelations About Airline Fees.”

Airlines for America, a trade group that represents the largest U.S. carriers, said air travel has become more affordable and that customers can choose what they want to pay for onboard.

“The report demonstrates a clear failure by the subcommittee to understand the value the highly competitive U.S. airline industry brings to customers and employees. Rather, the report serves as just another holiday travel talking point,” the group said.

The report also criticized budget airlines Spirit and Frontier, saying they paid gate agents $26 million between 2022 and 2023 to “catch passengers allegedly not following airline bag policies, often forcing those passengers to pay a bag fee or miss their flight.”

Spirit said in a statement that it is “transparent about our products and pricing, our airport policies ensure Guests are treated fairly and equally, and we comply with all tax laws and regulations.”

Frontier said that the commissions for gate agents are “simply designed to incentivize our team members to ensure compliance with bag size requirements so that all customers are treated equally and fairly, including the majority who comply with the rules.”