No one was hurt in any of the incidents. But the loud noises, aircraft shaking and flames as well as the clustering of events have tapped into passengers' anxieties about flying and prompted Allegiant officials to pledge better communication with their customers.

The incidents generated news coverage in Fresno and Pennsylvania and e-mails from upset passengers that were published online. They demonstrate how even an airline with a safe and profitable system can have trouble keeping pace with the spread of information, particularly if the information is dramatic, like a first-hand account of a troubled commercial jet flight.

"I heard a loud explosion, loud enough to freak everybody out," said Michael Brush, 33, of Las Vegas about his Allegiant flight on June 21. "The whole plane shook, people started getting frantic."

Brush said there was light smoke in the cabin and some passengers panicked.

"Everybody was sort of unnecessarily frantic," he said.

Airline personnel didn't make Brush and his girlfriend feel any better, he said. After the plane landed, Brush said a worker who greeted passengers said such an incident had never occurred at Allegiant before. Later, Brush was angry when he learned a similar incident had occurred just two months earlier.

"He wasn't honest with me," Brush said.

In the incident on April 26, an Allegiant aircraft was en route from Fresno to Las Vegas when passengers reported a loud noise. An engine had failed and the aircraft returned to the airport safely.

The third incident occurred Sunday in Allentown, Pa.

In that case, an engine sucked in a piece of tread that had separated from a tire, causing flames to shoot out of the engine before the crew idled it and headed back to the airport.

No one, including the Federal Aviation Administration nor independent aviation experts, suggests Allegiant, which safely flew more than 10,000 scheduled flights in the past three months alone, is to blame for the incidents.

The engine type involved, JT8D-200-series model manufactured by Pratt & Whitney, is considered high-quality and is in use on nearly 2,500 jets worldwide, including nearly 1,300 in the United States. Since 1992 the engine series has generated just 35 accident/incident reports with the FAA.

In most of those incidents the engine in question was shut down and the aircraft returned safely with one engine.

Two passengers were killed in 1996 when a JT8D-219 engine on a Delta Airlines aircraft broke up during takeoff from a Pensacola, Fla., airport and struck the fuselage, according to the FAA and news reports from the time.

Allegiant has had no such problems and its performance compares favorably to the industry.

In the second quarter, Allegiant's cancellation rate for any reason, mechanical or otherwise, was 0.3 percent, compared to the 1.45 percent overall rate at the nation's top 20 airports. Allegiant also has a contract with American Airlines to provide heavy maintenance on its engines, meaning Allegiant workers don't open the engines themselves.

The engines are maintained on a regular schedule and each one is also tracked for trends that can prompt additional maintenance.

"You have the schedule set in place, but you also want to keep an eye on everything proactively," said Allegiant spokeswoman Tyri Squyres.

No cause has been determined for the April 26 and June 21 engine failures in Fresno. Squyres said the engines will be inspected by independent, third-party experts.

Aviation consultant Michael Boyd of Evergreen, Colo., said the cluster of incidents doesn't indicate a lack of safety, but does show how important it is for airlines to promptly respond to any incident that upsets customers before they transmit their fears and anger to the world by text message, e-mail or cell phones that can broadcast problems in the sky before an aircraft has returned to the airport.

"Then you have an airline with a superb track record of customer service being made to look like it is a Third World operator, which is unfair," Boyd said. "In this day and age you have to be a whole lot more savvy in dealing with customers."

With so many instant communication options, passengers can report dramatic in-flight problems so quickly that they can be broadcast globally even before airline officials know they occurred.

Images from a Jan. 15 U.S. Airways flight that landed on the Hudson River were posted online and picked up by national news networks by the time rescuers were arriving.

That type of communication puts airline flight crews in the position of not only having to manage the incident, but also on the front lines of how that incident will be perceived by large audiences.

"We have huge gossip channels now that spread around now," Boyd said. "That is another challenge airlines, and any business, have to deal with."

The Allegiant incidents, individually and combined, were enough to generate coverage by a Fresno television station and cause passengers to question the airline.

"This is crazy. ... I can't believe it happened again," one of the passengers on the April 26 flight wrote to Mike Scott, a CBS news anchor in Fresno who reported the incidents in detail on his blog, including 12 excerpts from e-mails and photos he received from passengers after the first mishap.

Several passengers from the April 26 and the June 21 flights complained they didn't receive enough information from crew to calm them during the incidents or to answer their questions afterward.

Mary Lucio of Fresno was on the June 21 flight. She said she and her husband were seated in the rear of the plane and, even though the pilot made an announcement to the cabin, she couldn't hear it over cabin noise. And she felt the information was insufficient.

"I just can't get this whole ordeal out of my mind; we couldn't sleep the whole night; our nerves are really bothering us," she wrote to Scott.

Another passenger from the June 21 flight who did not want her name used said she has tried to contact Allegiant for an explanation but has yet to hear back.

She said she "can't put this behind me until I know the facts," and added that a phone number an Allegiant worker told her to call the company went to a voice mail that had no name or identifying information.

The passenger praised the cockpit crew for landing the plane safely but said after six calls to the Allegiant number no one from the company has called her back.

Squyres said in addition to multiple third-party inspections of the engines in question, the airline is reviewing its communication procedures in light of the incidents.

"Based on the first incident in Fresno, we started to review our procedures, duties and communications strategy," Squyres said. "We implemented many changes in the way we communicate with our customers on the second Fresno flight and in Allentown. We recognize that we still have work to do in this area, and are looking at this very closely to provide better support to our customers."

Contact reporter Benjamin Spillman at bspillman@reviewjournal.com or 702-477-3861.