In a 55-page report, the majority staff of the Senate Permanent Subcommittee on Investigations released on Tuesday its findings after a year-long inquiry into five U.S. airlines’ ancillary fees, which the report said have led to higher costs and worse experiences for consumers and, in some cases, tax avoidance by the airlines.

U.S. Sen. Richard Blumenthal’s report detailed how five airlines profit through these fees, alleging they do so at the expense of travelers

Airlines have raked in billions of dollars by charging extra to select a seat and some airlines paid workers incentives to encourage charging more for baggage fees, according to previously undisclosed data in a new Senate subcommittee report.