Airlines Add Fees _ And Some Fees On Top Of Fees

But that began to change last spring. Spiking jet fuel prices and passenger resistances to higher fares started airlines looking around the cabin for things they could charge extra for.

Passengers are finding it's a lot easier for the airlines to add the fees than to take them away.

"They're going to keep nudging them up until they run into market resistance," said Ed Perkins, a contributing editor at the Web site Smarter Travel.

That's what happened at US Airways. It tried for seven months to charge for soda and water but gave up in March after no other airlines took up the idea. And Delta scaled back a plan to charge $50 to check a second bag on all international flights. Instead, the charge will apply only on flights to Europe.

United has been a leader in finding ways to charge passengers separately for things. Some are for perks coach travelers used to get for free, like food. Others are new services altogether, like United's door-to-door luggage service via FedEx.

Airlines say fees are part of "a la carte" pricing that allows them to hold the line on fares. Rather than charge higher fares to everyone, they say, passengers can pick and choose the extras they want to pay for.