Airlines have doubled baggage fees and other add-ons since the extra charges took off in 2008, according to a report released by an airline consultant.
The review by Wisconsin-based IdeaWorks found that 47 airlines charged $21.5 billion for ancillary fees in 2010 -- up 96 percent in just three years.
For some smaller airlines, the fees -- for everything from baggage to in-flight food -- now account for nearly a third of all the money they bring in, the report said.
The top airline was United Continental, which raked in $5 billion last year in such fees.
Delta took in $3.7 billion, followed by Fort Worth-based American, which collected $1.9 billion.
American spokesman Tim Smith said the figure was only a slight increase over the previous year.
"It's an important part of our revenue," he said. "The old days of 'one price fits all' is not the business model these days."
Smith said customers who don't want extra services don't have to subsidize those who do.
"There's a lot of price-conscious travelers," he said.
But the fees remain unpopular with many passengers.
"We get nickel-and-dimed everywhere," complained one woman at Dallas/Fort Worth International Airport.
"It's horrible," said another traveler. "I think it's just a crime that they can hold you hostage like this. You don't get a choice."