U.S. airlines earned $2.6 billion in fees and frequent flier mile sales in 2014, an 18.7 percent increase from 2013,  according to an annual report by consultancies IdeaWorks and CarTrawler.

That represents the eighth consecutive year that carriers saw substantial revenue ancillary to ticket sales. Globally, ancillary revenue soared more than 20 percent to $38.1 billion.

“Ancillary revenue is an increasingly important indicator of commercial success, and a major contributor to the bottom line of airlines across the globe,” said Michael Cunningham, CarTrawler’s Chief Commercial Officer, in a statement.

Related: 6 Sneaky Fees that Are Making Airlines a Bundle

By passenger, additional revenue grew by 8.5 percent to $17.49. Low cost carriers increased ancillary revenue by 32.8 percent for the year, or $2.9 billion.

Ten airlines earned two-thirds of the ancillary revenue, led by United Airlines, American/U.S. Airways, and Delta. Delta brought in $350 million through its Comfort Plus program, which allows passengers to pay extra for more legroom and priority boarding.

Among passengers’ most hated fees are checked bag fees. Airlines typically charge $25 for the first bag, $35 for the second, and more than $100 for a third bag.

As frequent fliers turn to branded credit cards as a means of avoiding fees, airlines are still earning money. Last year, American’s Citibank-issued credit card, which gives consumers one free checked bag and priority boarding, yielded an additional $624 million for the carrier last year.

The additional fees are not improving the customer experience. More than 60 percent of consumers surveyed by the U.S. Travel Association in March said they were frustrated with air travel generally.