A new report shows the nation's airlines are making a killing by tacking on extra fees.

IdeaWorks says fees for early boarding, extra leg room, on-board snacks, and checked luggage totaled a stunning $27 billion last year.

That's up 20 percent in just one year's time. The study says the most aggressive airlines created more than 20 percent of their revenue through "a la carte fees."

United Airlines, Delta, American and Southwest led the way in the total amount of non-fare revenue collected in 2012.