FORT WORTH, Texas — After enjoying a summer of heavy and profitable travel demand, the airline industry has hit a patch of turbulence that could cause some uneasy fliers to reconsider taking to the skies.

Several weeks of security-related incidents, including a diversion of a US Airways flight yesterday after a threatening note was found aboard, have put concerns of airline terrorism back in the spotlight.

And the crash Sunday of a Comair Airlines flight near Lexington, Ky., that killed 49 people ended a nearly five-year stretch without a major domestic airline crash.

"For some people who are on the fence in terms of their comfort with flying, the incidents we've seen could potentially get some of them to stay home, or opt for driving at least a portion of the distance," said travel analyst Henry Harteveldt of Forrester Research.

The good news for the airlines is that most of the summer leisure-travel season has passed, analysts say. Safety and security concerns tend to affect tourists more than business passengers, which will likely minimize the impact on the industry.

And frequent fliers have become used to security-related hassles at the airports, airline consultant Darryl Jenkins said.

"These things drive you batty, and everyone hates them," he said. "But people adapt and plan for them, and at the end of the day, they're just a pain in the rear, but you deal with them."

Investors appeared unconcerned yesterday, bidding up airline stocks as oil prices declined. Shares of AMR Corp., parent company of American Airlines, rose 52 cents to close at $19.92. Southwest Airlines climbed 34 cents to $17.29 per share. And Continental Airlines was up $1 to $23.96 per share.

The latest round of problems for the industry began Aug. 10, when British authorities said they had thwarted a plot to blow up passenger jets between London and the United States.

The Transportation Security Administration banned most liquids and gels in airline cabins, resulting in an unexpected surge in checked baggage and longer security lines at some airports.

In subsequent days, a spate of scares made the news as several flights were diverted because of disruptive passengers or suspicious objects such utility knives, found aboard.

An American Airlines flight from Manchester, England, to Chicago was diverted Friday to Bangor, Maine, after authorities on the ground reported a threat.

Then Sunday's crash of Comair Airlines Flight 5191 was the worst airline accident since 2001.