U.S. airlines collected more than $12 billion from seat fees

Fees to select seats or to sit in rows with a few extra inches of legroom have become big business for airlines, according to a Senate subcommittee report released Tuesday.

Five U.S. airlines collected $12.4 billion from such charges from 2018 to 2023, according to the report. Checked bags-the airlines’ biggest source of revenue beyond tickets themselves-brought in about $25 billion over that stretch for those carriers.

Tuesday’s report tallied seat fees from United, Delta, American, Spirit and Frontier. Delta’s lucrative Comfort+, which the airline sells as a different type of ticket, wasn’t included in the tally.

Airlines have become adept at slicing their cabins into narrower niches and offering an ever-expanding menu of a la carte options, even within coach.

But the report, which comes after a year-long look into airline practices, said the proliferation of fees has made the process of buying tickets more opaque.

The report recommended the Transportation Department collect more granular data on seat fees like it does for baggage fees. It also criticized Spirit and Frontier for offering commissions for upselling or catching passengers trying to skirt carry-on bag charges.

The two discount airlines denied to the subcommittee staff that policies were being abused. Frontier said in a statement that its goal was to ensure compliance with bag policies so all customers are treated fairly.

Airlines for America, which represents the largest U.S. carriers, said airlines are giving customers more choices and that ticket prices, even including fees, are at historic lows.

The Biden administration has sought to crack down on so-called “junk fees” across a range of industries. Airlines have pushed back against some proposals.

Write to Alison Sider at alison.sider@wsj.com