A U.S. Senate panel is taking aim at airlines and their growing use of fees for things like early boarding and better seats.

Five major U.S. airlines will be called to testify on Capitol Hill on Wednesday over rising ancillary fees paid by passengers.

Executives from United, Delta, American Spirit and Frontier airlines will testify Wednesday to defend billions of dollars in airline seating fees at a U.S. Senate subcommittee hearing.

The U.S. Senate Permanent Subcommittee on Investigations will hold a hearing Wednesday with five major airline executives about the rise of ancillary or “junk" fees and its impact on consumers.

Executives from American, United, Delta, Frontier and Spirit are set to testify before a Senate panel Wednesday about their seating fees.