Early February, Delta Air Lines Inc and American Airlines raised most domestic round-trip fares by US$10 because of higher fuel costs.

Bloomberg News reported that the move marks the third attempt at a broad fare increase this year by major United States-based airlines. Delta boosted fares late on Feb. 1. Alaska Air Group Inc also matched the increase, said Jamie Baker, a J.P. Morgan Securities Inc analyst.

"We ascribe a high probability of success to this effort, if so marking the second broad increase of 2007 out of three attempts," Baker said in a report.

UAL Corp's United Airlines, Northwest Airlines Corp, Continental Airlines Inc and US Airways Group Inc said they were studying the increase. To stay competitive, airlines generally drop fare boosts that aren't matched. Airlines are taking advantage of higher travel demand and tighter US capacity to raise prices and help offset higher operating costs.

US carriers successfully raised fares on January 11. A second attempt led by United on January 19 failed after some rivals didn't adopt the higher prices.

"We continue to face increased costs, including fuel," Betsy Talton, a spokeswoman for Atlanta-based Delta, said via e-mail. "In the third-quarter alone, Delta paid nearly US$250 million more for fuel than the same time last year."

Delta hasn't reported results for the 2006 fourth quarter. The airline's fare increase came one day after its bankruptcy creditors committee rejected a US$9.75 billion hostile takeover bid from US Airways. Delta plans to exit bankruptcy protection in the first half of this year as an independent airline.