Airlines want you to fly the fee-filled skies

— -- Airline fees keep piling up for passengers, with several carriers imposing new charges and industry observers predicting more to come.

Southwest, which still doesn't charge to check bags but hasn't ruled out doing so in the future, says the new boarding fee could bring in tens of millions of dollars a year in revenue.

The latest fees are unlikely to be the last as airlines race to find ways to boost the bottom line at a time when travel has dropped off significantly.

"I think they're going to continue to look at anything that's possible to unbundle and charge for," says Kevin Mitchell, chairman of the Business Travel Coalition, an advocacy group for corporate travel departments.

Mitchell says some analysts predict the industry could earn more than $2 billion a year from extra fees. But he believes there could be a backlash from fee-weary fliers.

"It's not without risk," he says. "Individual travelers feel they're being nickeled and dimed. How much can consumers absorb? So far the airlines have been lucky, but they might be getting pretty close."

Among the new fees:

•Continental is charging $50 to check a second bag at the airport for economy travel between Europe and the U.S. The new fee applies to tickets bought starting Aug. 27 for travel starting Sept. 15. Fees will be $5 less if the second bag is checked and paid for online. The first checked bag remains free.