WASHINGTON (AP) — Several congressional Democrats are reviving legislation to regulate fees that airlines charge for things such as checking a bag, changing a flight or picking a seat.

The legislation would require that fees be “reasonable and proportional” to the airline’s cost of providing the service. It will also require airlines to let children under 14 sit with family members at no extra charge.

One of the bill supporters, Sen. Richard Blumenthal, D-Conn., accused the airlines of “robbery in the skies — taking fees and charges for stuff that costs them nothing.” He said airlines can charge high fees because Congress hasn’t stopped them from doing so.

Airlines “offer a robust variety of air-travel options, giving passengers the ability to choose the services that best fit their individual needs and preferences,” said Carter Yang, a spokesman for the trade group Airlines for America.

Prospects for the legislation are uncertain. Similar bills have failed to get through Congress, and one of the most despised fees has largely disappeared: Most U.S. airlines dropped ticket-change fees after the pandemic devastated air travel last year.

The fees, which ranged up to $200 for changing or canceling a domestic flight, made some consumers reluctant to book a flight during uncertainty around COVID-19 rates and travel restrictions.

Most airlines, however, have kept fees to check a bag — usually starting around $30 — or board the plane early or select certain more-desirable seats. U.S. airlines raised $5.8 billion from bag fees alone in 2019, falling to $2.8 billion in 2020.