Airlines have made billions of dollars from so-called “junk fees“, charging passengers extra for selecting a seat or carry-on bag, according to a Senate Subcommittee report released Tuesday, according to CNN.

From in 2018 to 2023five US airlines made more than $12 billion just from seat selection fees, a “separate” cost that used to be included in the ticket price. The report said that in 2023, United Airlines charged up to $319 for seats with extra space, Spirit Airlines up to $299, Delta Air Lines up to $264, Frontier Airlines $141 and American Airlines up to $140.

The report said airlines are even incentivizing employees to spot passengers trying to avoid carry-on fees. Frontier and Spirit paid $26 million in 2022 and 2023 to encourage employees to spot passengers who violate baggage policies, forcing them to pay fees or miss their flight.

Frontier confirmed the practice, explaining that the incentives for gate agents are meant to ensure compliance with baggage size policies and treat all passengers fairly.