WASHINGTON -- In the last two years, airlines have collected $7.9 billion for baggage fees, reservation changes and other ticket add-ons from customers often unaware of the true price of their travel.

With airline fees climbing even higher this year, the Government Accountability Office today said today that companies should provide more information so travelers know what flights will cost when booking them.

"Making complete, clear and uniform information on airline fees available through travel agents and airline websites would enable passengers to make fully informed choices," the report from Congress's investigative arm concluded.

At a House hearing this afternoon called to examine the fees, a powerful legislator went farther by warning airlines that could face government curbs on the fees.

Rep. James Oberstar, D-Minn., chairman of the House Transportation and Infrastructure Committee, said that people often complain to him about fees for items such as blankets and headphones as well as for luggage.

He said a European carrier tried unsuccessfully to impose a fee for using the rest room.

Addressing his words to airline executives, Oberstar said: "If they don't exercise restraint, there's going to be an outcry of complaint from the traveling public and there are going to be regulations that you don't like."

Rep. Jerry Costello, D-Belleville, chairman of the Aviation subcommittee, said he worried that the fees charged are excessive. 

Costello observed that by charging untaxable fees that traditionally were part of ticket costs, airlines are diverting revenues that support the Federal Aviation Administration and airline safety improvements.

The GAO report said that airlines have recently begun charging for services such as Internet connection, lounge access and multiplying frequent flyer miles.

Gerald Dillingham, a GAO investigator, testified at the hearing that all the fees "have become an important part of the profit and loss statement of many airlines."

Dillingham also said that the fees "are not assessed equally and are not fully transparent."

Robert Rivkin, the Transportation Department's top lawyer, said that "the proliferation of these fees and the manner in which they are presented to the public can be confusing and misleading."

He said that his agency planned to propose rules governing airline fees by the end of the year.