Southwest reported Thursday that its third-quarter profit more than tripled from a year ago. Continental posted higher earnings thanks to heavy traffic on international routes.

And people are still lining up to fly, even with several rounds of recent fare hikes. United Air Lines made the latest increase, adding $20 per round trip on nearly all its domestic flights, and was quickly matched by Delta Air Lines Inc. and by Continental on some routes.

The higher fares don't seem to be discouraging travel. Weakness in parts of the economy such as housing don't seem to be having much effect either — Continental executives said advance bookings for travel the rest of the year were ahead of last year's pace.

But the fuel price outlook is much worse than it was just a couple of weeks ago. Oil prices surged again Thursday, moving closer to the $90 per barrel barrier. Fuel is typically an airline's second biggest cost, after labor.

"Long term, the big concern is the economy, but right now fuel is the monkey on their backs," said Ray Neidl, an analyst for Calyon Securities. "The airlines would be producing spectacular results if oil weren't at $90."

Airline stocks fell in response to the latest increase in oil prices. Shares of Continental fell $1.30, or 3.6 percent, to end at $34.93; and Southwest shares lost 23 cents, or 1.6 percent, to close at $14.33 Thursday.

Of the airlines that have reported earnings this week, most have been in line with Wall Street expectations, although Continental beat forecasts.

Houston-based Continental said it earned $241 million, or $2.15 per share, in the three months that ended Sept. 30. That compared with $237 million, or $2.17 per share, a year earlier, when the company realized a $92 million gain on an investment sale.

Continental would have earned $2.25 per share after excluding a special charge for a pension plan settlement. Analysts, who usually exclude such charges from their forecasts, had expected Continental to earn $2.17 per share, according to a survey by Thomson Financial.

Revenue rose nearly 9 percent, to $3.82 billion. Sales grew 22 percent on trans-Atlantic flights and 10 to 11 percent on other international flights — but just 7 percent in the United States.

The average flight was 84.3 percent full, 1.6 percentage points higher than a year earlier. That helped overcome a 4.3 percent bump in fuel costs.

"I never thought we would use the terms 'record oil' and 'record operating results' in the same quarter," said Chairman and Chief Executive Larry Kellner.

Continental officials said they intend to keep growing the airline, including expansion of a hub at Cleveland from about 250 daily flights now to more than 300 by early next year. They said cuts by other carriers at nearby Pittsburgh and Cincinnati had opened the door for growth in Cleveland.

Dallas-based Southwest, the nation's biggest discount carrier, said net income for the third quarter jumped to $162 million, or 22 cents per share, compared with $48 million, or 6 cents per share, a year earlier.

Analysts surveyed by Thomson Financial had expected 21 cents per share. Southwest and several analysts said the airline had hit that target, after excluding one-time charges.

Revenue rose 11 percent, to $2.59 billion, as Southwest filled 76.6 percent of the seats on the average flight, a record.

But Southwest's costs as a ratio to capacity rose 3.9 percent, largely because of higher fuel prices.

Airlines try to hedge their fuel costs, and none have done it better than Southwest, which locked in lower prices on 70 percent of the fuel it used last quarter. Still, that strategy is losing its effectiveness as oil prices climb higher and stay there.

The rising cost has forced Southwest to raise fares and slow its growth rate. Analysts and investors cheer when airlines cut capacity, because that tends to drive up prices — and profits.

Jamie Baker, an analyst at JP Morgan, questioned how Southwest could justify any capacity growth because profits are about the same as they were in the late 1990s, even though revenue has doubled since then.

CEO Gary Kelly said expansion made Southwest a stronger competitor. He believes the company can hit profit targets by increasing revenue 10 percent a year while managing fuel costs.

"After a year or two, if we're not on pace to generate that kind of return, than I think it would argue that you stop investing," Kelly said.