The Department of Transportation said revenue from so-called ancillary fees rose 42 percent to $7.8 billion in 2009. The biggest chunk of that came from checked baggage fees, which were introduced in 2008 when oil prices soared and evenutally reached $147 per barrel.
Besides checked bags, other fees include those for reservation changes, pet travel and mileage sales.
United and Continental, which on Monday announced plans to combine to form the world's biggest airline, were sixth and seventh among carriers in fees collected. United took in $619.5 million in fees, Continental $539.7 million.
Delta, currently the world's largest airline, collected the most revenue from fees at $1.65 billion. American was second, followed by US Airways.
Southwest doesn't charge for the first two checked bags, but it still earned fourth place in the fee rankings. Southwest, which carries more passengers than any other U.S. airline, charges $50 for a third checked bag, as well as fees for pets traveling in the cabin and unaccompanied minors.
Smaller discount carrier Spirit Airlines isn't in the top 10. But 21 percent of its total operating revenue came from extra fees, more than any other carrier. Besides bag fees, Spirit charges for seat assignments, drinks, snacks, pets and kids traveling alone. It will start charging as much as $45 for a carry-on bag as of Aug. 1, a first for a U.S. airline.
In the last three months of the year, revenue from airline fees rose 18 percent to at least $1.9 billion. Bag fees totaled $736 million in the October-to-December period.