WASHINGTON A U.S. Senate subcommittee on Monday said it was opening an investigation into airline fees for baggage, seat selection, ticket changes and other services.

Senator Richard Blumenthal, a Democrat who chairs the Permanent Subcommittee on Investigations, wrote the CEOs of American Airlines, United Airlines, Delta Air Lines, Spirit Airlines, and Frontier Airlines seeking a detailed breakdown on how much they collect from each fee, the reason for charges and the costs to supply each service.

(Reporting by David Shepardson; Editing by Chris Reese)