United and Jet Blue recently increased their checked bag fee to $30. Nobody likes paying for things we didn’t pay for in the past, like checked luggage. A bill in the U.S. Senate would limit airlines’ checked bag and other fees, which topped $7 billion in 2016. But economics suggests that bag fees can make air travel more efficient, not merely extract money from travelers.

American was the major airline to charge for checked bags in 2008. The fee rose from $15 initially to $25, and almost all airlines except Southwest use this fee, while some regional airlines even charge for carry-on bags. Airline credit cards and frequent flier programs often allow free bags.

It is tempting but inaccurate to say that until 2008 passengers did not pay for checked bags. Carrying luggage is costly: airlines need larger planes with cargo space and must hire baggage handlers, while extra weight requires extra jet fuel. U.S. airlines are businesses and cannot lose money for too long. Revenue must at least cover costs, with or without bag fees.

Prior to 2008, the price of tickets covered the cost of carrying bags, averaged across all fliers. If passengers checked on average one bag each, perhaps $25 of the ticket price would have covered baggage costs. Fliers with many bags would prefer paying a ticket price covering the average number of checked bags, while passengers without bags effectively paid for others’ luggage.

Travelers now must pay for checked luggage. This should make air travel more efficient overall. Previously passengers might have checked a bag with contents providing only $10 or $20 of value to them. If the $25 bag fee approximately equals the airlines’ cost of transporting bags, a bag valued at $10 will no longer fly, which is good because it was not worth the cost.

My points about bags apply to other airline services like meals and beverages. If airlines do not charge for alcoholic beverages or meals, ticket prices must cover these costs. First class passengers still receive such “freebies” but their expensive tickets certainly cover the costs.

Should airlines then charge for everything, including the reading light or the lavatory? Two factors limit charging for everything. One is the cost of restricting access and collecting money from willing users. Electronic payments make collecting fees easier, but lavatories would need to be accessible only after paying. Negative reactions from passengers also matter. People do not like being nickel-and-dimed for every little thing; losing a frequent flyer due to a $3 fee is bad business. Social media now amplifies customer complaints.

Until 1978, the Civil Aeronautics Board (CAB) regulated U.S. airlines, including the routes airlines could fly and fares. Forty years of deregulation have reduced fares by 50 percent in exchange for few extra services. Today, most Americans can fly at least occasionally; under government regulation, flying was primarily for business travelers and the well-to-do.

Senators Markey of Massachusetts and Blumenthal of Connecticut have introduced the Forbid Airlines from Imposing Ridiculous Fees, or FAIR, Act to limit fees of any sort, including for changes or cancellation. Rebooking fees run from $75 to $300 plus the difference in price of the flights. Cancellations can result in seats going unused on high demand flights and thus cost airlines. While these fees seem high to me, airlines know much more about their operations and costs than I do.

Competition between airlines for passengers is a better way to keep fees reasonable, fares low, and service quality high. Southwest advertises that bags fly free, and airlines seeking competitive advantage will undercut any excessive fees. If the Senators want to assist the flying public, they should address access to gates at our nation’s airports, a factor which economists find limits competition.

Travelers will pay for checked luggage, either through fees for each bag or higher ticket prices. While it is nice when someone pays for us, air travel is more efficient when we each pay our own way.

Daniel Sutter is the Charles G. Koch Professor of Economics with the Manuel H. Johnson Center for Political Economy at Troy University.