Airlines are being warned to show some restraint when it comes to all of those additional fees they’re charging for things like checked bags, blankets and pillows, and prime spots in boarding lines.

At a House hearing today, Democratic congressman James Oberstar of Minnesota warned that the public will push back, and that “Congress will act,” unless the industry limits those fees.

The airlines say passengers benefit from the fees, because airlines are able to keep ticket prices down while charging consumers only for the services they use.

A spokesman for the Air Transport Association says, “There is no reason why one passenger should subsidize another for a service he or she doesn’t consume.”

But the Government Accountability Office is out with a report saying that the fees make it hard for air travelers to shop for the best fare. A GAO official told the hearing that airline fees “are not very transparent.”