Several major US airlines and their lobbying group sued the US Transportation Department over new regulations mandating up-front disclosure of certain fees, in a fight over rules the agency says could mean big savings for travelers.

The lawsuit was filed Friday at the 5th US Circuit Court of Appeals by industry trade group Airlines for America and the carriers, including American Airlines, Delta Air Lines, United Airlines and JetBlue Airways. They claim the department overstepped its legal authority in issuing the new requirements and called them “arbitrary, capricious” and “an abuse of discretion.” 

Airlines for America called them “a bad solution in search of a problem.”

The final rules, unveiled last month, require carriers and ticket agents to clearly communicate their extra charges up front for checked luggage and carry-on bags and for canceling or changing reservations. The department said at the time that they would save fliers more than half a billion dollars a year by helping them avoid surprise fees.

The legal battle will be a key test of new consumer protections sought by the Transportation Department. The agency has also issued final rules requiring airlines to provide automatic refunds if flights are canceled or significantly delayed. It has plans, at various stages of drafting, for regulations that would expand rights for passengers who use wheelchairs and to allow parents to sit with their children without being charged a fee. 

Airlines for America said in a statement that the carriers already provide fee disclosures and that the new rules “will greatly confuse consumers who will be inundated with information that will only serve to complicate the buying process.” 

The Transportation Department vowed to fight the suit.

“We will vigorously defend our rule protecting people from hidden junk fees and ensuring travelers can see the full price of a flight before they purchase a ticket,” department spokesman Sean Manning said in a statement. “Many air travelers will be disappointed to learn that the airline lobby is suing to stop these common-sense protections.”

The suit was reported earlier by Reuters.

The case is Airlines for America v. Department of Transportation, 5th US Circuit Court of Appeals (New Orleans).