The price of an airline ticket has remained generally consistent in recent years, but have you noticed those extra charges sneaking slowly upward?
That's more than double the amount airlines made from extras in 2009.
Of all carriers studied around the world, United made the most total dollars -- over $5 billion -- in ancillary revenue last year. Next came Delta, American and Southwest.
For the study, "ancillary revenue" was defined as "revenue beyond the sale of tickets." That could include charges for priority check-in, assigned seating, and food and beverages offered on the plane.
Spirit is the airline whose ancillary revenue made up the most of its total revenue for the year: 38.5%. This came firstly from baggage fees and secondly from a "passenger usage fee," which is when you're charged for booking your ticket anywhere besides the airport. It's the same obscure fee that resulted in a nasty lawsuit for Spirit last year.
Other sneaky charges with big payoffs include Southwest's EarlyBird Check-In, which earned the airline $161 million last year (and more money is likely on the way, since their famous no-show policy is no longer).
United made over $2 billion from selling frequent flyer miles.
And according to the study, Qantas gets an average of $56.21 in extra revenue for every passenger. This probably doesn't come entirely from in-flight fees, rather it's made when the airline sells frequent flier points to program partners.
However airlines make their money, some argue a few extra fees are good for keeping ticket prices constant in a struggling economy. Others see the charges as crafty and unfair.
As Charlie Leocha, director of the Consumer Travel Alliance, told NBC News:
“This is $27 billion of deception. The growth in ancillary revenue streams makes it more important than ever today that the airlines begin disclosing these ancillary fees at all points where they sell their airfares.”