HOUSTON -

If you've flown recently, you've probably been slapped with an extra fee, and all those fees are adding up to big profits for the airlines.

A new study found those charges are actually creating billions in revenue.

The report by consulting firm IdeaWorks and sponsored by travel technology firm Amadeus looked at 50 airlines around the world. They found the airlines' extra costs took in $22.6 billion in 2011. That is 66 percent more than than the $13.5 billion the airlines made in 2009.

The extra charges started after the recession.

United, Delta, American and Qantas made most of the profit.