The big U.S. airlines are raising base fares by $10 per round trip with the busy summer travel season just around the corner.
United, Continental, Delta and American raised prices, but some of the low-cost carriers had not matched the increases by Friday afternoon.
The airlines face sharply higher costs for fuel, one of their biggest expenses. They have pushed through at least six broad price increases this year, but the last two in March failed when some airlines declined to go along.
"It's the good old college try — if it doesn't work, you try again," said Tom Parsons, CEO of travel website BestFares.com. "One week it's going to stick."
United and Continental raised prices Thursday night, said spokeswoman Julie King. Both are owned by United Continental Holdings Inc., the nation's largest airline operator.
US Airways, Southwest and AirTran Airways said they had not matched the increase.
The $10 increases applied to heavily traveled routes and to some between smaller cities — as different as Boston-Los Angeles and Portland, Ore.-Savannah, Ga.
U.S. airlines raised base fares twice in January, three times in February and once in March. As a result, the price of some trips has risen 20 percent in the past year, said Parsons, who cited transcontinental routes including Boston to Orange County, Calif.
Separately, airlines also have increased the price of premium tickets typically purchased only by a small number of corporate fliers and luxury travelers.
Base fares don't always reflect what passengers actually pay to fly. Airlines frequently run sales at deep discounts. This week, AirTran started a 3-day sale that was matched by many other airlines. The deals expired Thursday night.
Airlines say they need to charge more to cover rising jet fuel costs. The spot price for a gallon of jet fuel hovered at $3.12 this week, up 52 percent from $2.05 in early September.
Many airlines try to ease the sting of higher fuel prices through hedging deals, such as buying options contracts to take fuel at a certain price. Those contracts can backfire, costing the airlines tens of millions, if the price of oil or fuel suddenly drops.