It could cost you even more to travel next spring and summer.

US Airways said Tuesday it will add a 5 percent surcharge to all U.S. flights on or after May 8.

Spokeswoman Valerie Wunder says the surcharge will protect the airline in case fuel prices or other costs increase.

Separately, Delta, Northwest and United confirmed that they bumped the surcharge on some busy days next March and April to $30 each way from $20 — and to $50 on the day after the Super Bowl.

Most major U.S. airlines have been losing money this year, and they're scrambling to add revenue with bag-handling fees and surcharges on heavy travel days.

Airlines have also been cutting unprofitable flights, which saves money and reduces the supply of seats on America's jetliners.

"The number of seats they've cut is allowing them to do crazy things," said Tom Parsons, CEO of discount travel site Bestfares.com. "They added bag fees and nobody blinked. They've got $150 (itinerary) change fees, and now the surcharges."

Parsons said consumers should expect higher prices next year, whether they're called fares or surcharges.

"There were a lot of bargains in 2009, but it looks like that's not going to happen in 2010," he said.

It wasn't clear Tuesday afternoon whether the higher surcharges would stick. Other major carriers including American and Continental had not matched them, Parsons said. Neither airline commented immediately. Airlines often roll back fare increases if competitors stick to lower prices.

The dates on which Delta, Northwest and United raised the surcharge to $30 include March 14, 20, 21 and 28 and April 5 and 11, according to Parsons. Representatives of the airlines confirmed the increases.

Wunder, the US Airlines spokeswoman, said the new 5 percent surcharge beginning next May was designed as a hedge against uncertain costs.

"We take more risk when we take bookings early," she said. "We don't know what the environment will be if fuel goes up or our costs go up because of schedule changes."