The airlines are at it again. The major U.S. carriers are trying to raise fares for the fourth time in a month, by $10 per round trip on many domestic routes, including Alaska and Hawaii flights. The airlines blame the rising cost of jet fuel.

Oil prices surged to a record high close Friday, above $57 a barrel, a sign of even higher prices for fuel, which accounts for about one-fifth of an airline's costs.

Delta Air Lines Inc. (DAL) and UAL Corp.'s (UAL) United Airlines led the way with increases of $10 per round trip Thursday night, and US Airways Group Inc. (UAIR), Northwest Airlines Corp. (NWAC) , AMR Corp.'s (AMR) American Airlines and America West Airlines matched the higher fares Friday, officials for the airlines confirmed.

Continental Airlines Inc. also raised its fares, according to several other carriers, but Continental officials did not immediately return calls for comment.

The carriers had raised fares three times in the past month, in steps of $10 to $20 per round trip each time.

The big carriers, however, avoided raising fares on some routes where they compete directly with low-cost carriers such as Southwest Airlines Co. and JetBlue Airways Corp., which did not match the latest increase.

"For peak summer travel, they're asking you to refinance your house," said Tom Parsons, who runs a discount travel Web site, Bestfares.com.

Parsons predicted that fares are headed even higher by Memorial Day because carriers have lost so much money and are now saddled with rising fuel bills.

Prices still vary widely depending on the amount of competition.

American has raised the price of a Dallas-Syracuse, N.Y. round trip bought 14 days in advance from $308 last year to $428, Parsons said. But American and others charge as little as $198 for a round trip between San Diego and Providence, R.I., a route flown by Southwest, he said.

Airline officials say they must raise fares to cover the rising cost of fuel. Last year, U.S. carriers spent an estimated $6 billion more for fuel than they did in 2003, and analysts have predicted large losses for the carriers again this year.

Airlines also have more pricing power because their planes are flying fuller.