Three Allegiant Air flights suffered engine problems in March

The last two springs have proven to be challenging for Allegiant Air and its passengers with a high number of aircraft breakdowns for its aging fleet of MD-80-series aircraft. And now, spring 2017 is getting off to a troublesome start.

Three Allegiant MD-83s suffered engine-related breakdowns in March that led to emergency landings.

A March 19 Allegiant Air flight out of the Orlando-Sanford airport may have flown up to eight minutes with a fire in its right engine after a fire-suppression system failed to extinguish it, an incident the National Transportation Safety Board confirmed it is now investigating.

TIMES INVESTIGATION: Thousands of people flew Allegiant thinking their planes wouldn't fail in the air. They were wrong.

The engine fire on Flight 636, bound for Dayton, Ohio, was first reported by the Tampa Bay Times last month. But new details about the pilots' inability to extinguish the fire are contained in a document called a "service difficulty report" that the airline recently filed with the Federal Aviation Administration.

The document said the fire did not go out until "right before touchdown," when the plane made an emergency landing at Dayton. Later, mechanics found evidence of fire or high heat. None of the flight's 163 passengers and crew were hurt.

Six days later, pilots on a different Allegiant MD-83 that departed Sanford-Orlando with 159 passengers and crew declared an emergency after a cockpit warning light indicated a fire on their right engine, according to a second "service difficulty report." The report said the warning on Flight 696, which was headed to Tennessee, was "immediately followed by (right) engine fire."

The fire warning light went off after pilots reduced power on the engine, Allegiant spokeswoman Jessica Wheeler said Thursday.

In that case, Wheeler said, no evidence of a fire was found on the engine after it was inspected by mechanics. "Preliminary inspection found no signs of smoke or fire," she said in an email. The FAA said the warning light came on due to hot air from a malfunctioning air duct.

Then on March 30, a third Allegiant flight declared an emergency when one of its engines would not produce full power during a climb.

Allegiant plans on retiring its MD-80-series aircraft by the close of 2019. The airline says the aircraft are safe but are nonetheless prone to mechanical difficulties that create operation problems and flight delays that inconvenience passengers. The airline flies about 49 MD-80s in a fleet of about 85 planes, 2016 figures show.

The airline is adding 12 brand-new Airbus aircraft to its fleet.

TIMES INVESTIGATION: In a first, Allegiant Air buying 12 new Airbus aircraft

"Passengers should know that their safety and the safety of our crew has always and will always be our singular focus," Wheeler said.

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Mary Rose Diefenderfer, a former principal inspector with the FAA and a retired airline pilot, said engine fires are particularly rare and said three incidents like these would have caused her to place an airline under additional scrutiny.

"I'd be alarmed and calling Washington to ask for teams of inspectors to look at the airline," she said. "Anytime you have to shut down an engine, that's a lot of risk."

The NTSB does not normally investigate incidents that do not involve injuries, though it can review serious incidents without them, especially cases of serious engine failures.

Contact William R. Levesque at levesque@tampabay.com. Follow @Times_Levesque.