A U.S. senate panel is calling on executives from five major airlines to testify during a congressional hearing in December over their growing use of "junk" fees to increase revenue. 

During the Dec. 4 hearing, titled "The Sky’s the Limit – New Revelations About Airline Fees," senior executives from American Airlines, United Airlines, Delta Air Lines, Spirit Airlines and Frontier Airlines will convene in front of the Senate Permanent Subcommittee on Investigations (PSI). 

Sen. Richard Blumenthal, D-Conn, the chair of the subcommittee, announced the hearing Tuesday just as the committee released the findings of its PSI Majority Report. The report highlighted how major airlines have increasingly used ancillary or junk fees to boost their revenue, which has driven up costs for consumers, according to Blumenthal.

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In the report, the subcommittee said airlines have increasingly charged separately for goods and services that were once included in the price of a ticket over the past two decades. It's a tactic known as "unbundling," and the subcommittee said it "has not lowered the cost of flying for consumers, who now face additional charges to fly with carry-on or checked bags or to sit next to their minor children." 

For instance, the report found that Frontier and Spirit paid $26 million to gate agents between 2022 and 2023 to catch passengers not following airline bag policies. The passengers are then forced to pay a bag fee or miss their flight, the report said. 

The report also highlighted how seat fees have risen, with United charging as much as $319 for an extra-legroom seat in 2023. 

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"Our investigation has exposed new details about airlines exploiting passengers with sky-high junk fees," Blumenthal said in a statement. 

During the hearing, Blumenthal said he will be asking the airline executives "to justify these practices." 

"As we head into the Thanksgiving weekend, we regret that travelers will be charged millions of dollars in fees that have no basis in cost to the airlines but simply fatten their bottom lines," he said. 
 

Some 79.9 million people will make trips at least 50 miles from where they live in the six-day span from Nov. 26, the Tuesday before Thanksgiving, and Dec. 2, the Monday following the holiday, according to recent projections from AAA. 

Airlines for America, a trade association representing the major U.S. carriers including American, Delta and United, told FOX Business that it's disappointed in the PSI Majority Report, claiming it "demonstrates a clear failure by the subcommittee to understand the value the highly competitive U.S. airline industry brings to customers and employees." 

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It also said these fees are "optional services that customers choose based on their own needs and desires" and that airlines already provide consumers with complete disclosure of all fees associated with air travel before they purchase a ticket.

The trade group also said ticket prices, including ancillary revenues, "are at historic lows." It said that average domestic round-trip fares, including ancillaries, were 14% lower in 2023 compared with 2010. 

Delta told FOX Business that the carrier has voluntarily responded to the subcommittee’s requests, which include providing documents, responding to numerous rounds of requests and follow-ons and providing a senior level employee and a subject-matter expert at the subcommittee’s request for an interview to discuss these fees. 

"Next to safety, Delta’s number one priority is taking care of our people and our customers and includes our commitment to providing a choice of fare products that best meets our customers’ specific travel needs," Delta said in a statement. 

Spirit Airlines said it has a "long history of offering affordable, low-fare flights, which has made travel more accessible for the public." 

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The carrier said it is transparent about its products and pricing and disagrees "with numerous statements and conclusions contained in the report." 

"With that in mind, we believe it's time to come together and discuss meaningful initiatives that would even the playing field between larger and smaller airlines to benefit all travelers, including those who rely on airlines like Spirit," the carrier said. 

American Airlines and United Airlines declined to comment. Frontier has not responded to FOX Business' request for comment.