ATLANTA — Heading into the Christmas holiday, some major carriers have raised airfares to offset added cost pressures.

American Airlines, a unit of Fort Worth, Texas-based AMR Corp., raised its ticket prices Thursday between $10 and $40 for roundtrip fares, depending on the miles traveled. Also Thursday, Atlanta-based Delta Air Lines Inc. raised its one-way fares by $10 in most domestic markets.

Asked about the American and Delta increases, UAL Corp.'s United Airlines, based in Elk Grove Village, Ill., said it filed a fare increase Thursday night. The filing was for a $10 roundtrip fare increase on most domestic flights, spokeswoman Robin Urbanski said.

Kurt Ebenhoch, a spokesman for Eagan, Minn.-based Northwest Airlines, said yesterday that the airline hadn't made a decision on raising its fares.

"We are studying American's increase," he said.

US Airways spokeswoman Andrea Rader said the airline also will raise prices. She said it would increase fares $5 each way for trips of 500 miles or less; $10 each way for trips between 500 and 1,000 miles; $15 each way for trips between 1,000 and 2,000 miles and $20 each way for any flight of 2,000 miles or more.

Rader said US Airways was raising prices "for the same reasons of other carriers: fuel costs."

In American's case, the increase doesn't apply to sale fares.

American spokesman Tim Wagner said the fare increase was necessary to offset higher fuel costs.

Wagner said jet fuel prices are about 15 percent higher than this time last year and spot fuel is about 40 percent higher than this time in 2004.