OCALA — Veteran aircraft mechanic Greg Marino worked at Allegiant Air for just two weeks before he quit because of what he said are the airline's dangerous maintenance practices.

Marino said mechanics at the airline's facility in Sanford often lapsed into bad maintenance habits. He said they failed to follow proper procedure in diagnosing aircraft problems and routinely misused a Federal Aviation Administration program that allowed planes, under some conditions, to fly with inoperative components or systems.

Marino said the airline needlessly delayed repairs in the push to keep planes flying, eroding the margin of safety.

Allegiant officials said the airline has an exemplary safety record and disputes reports of inadequate maintenance. They have blamed the pilots' union — in bitter contract negotiations with the airline — for drumming up unfounded concerns about safety as a negotiation ploy.

Marino said he could not remain part of a system that was so poorly managed.

"So I fired Allegiant as my employer," Marino, 57, said during an interview at his Ocala home. "I didn't give them two weeks' notice. I wasn't going to spend 10 more minutes there. The bottom line for me was that they were operating a dangerous safety culture. I don't stay where this kind of nonsense goes on."

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Allegiant spokeswoman Kim Schaefer said confidentiality concerns prohibited the airline from discussing Marino's employment. But upon the mechanic's departure, he got this email from Kimberly Newton, Allegiant's corporate recruiter:

"I am sorry that this happened because I truly believe that you are a top notch person. If you ever need a letter of reference I will be more than willing to let them know that you are a GEM in this industry. You are a truly remarkable person from the short time that I have known you!"

Schaefer said Allegiant maintains "numerous channels through which any employee can bring attention to safety concerns," which "offers a systematic and non-punitive method for pilots, flight attendants, maintenance … to voluntarily identify and report safety concerns."

Still, 2015 was a challenging year for Allegiant, the budget airline based in Las Vegas whose flights account for 95 percent of record-breaking passenger traffic at St. Pete-Clearwater International Airport. Reports of emergency landings due to mechanical issues, including three in Pinellas County last summer, have dogged Allegiant.

In the last week of 2015 alone, five Allegiant flights leaving Florida made emergency landings due to mechanical issues, and four of those flew out of Sanford, where Marino worked. One of the five took off from St. Pete-Clearwater.

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Marino retired in 2011 from US Airways after having spent most of his 35-year career at the airline or its corporate predecessors. Marino, however, said he was bored by retirement, so he eventually applied for a job at Allegiant and was hired starting Oct. 12, earning $24 an hour.

But he said he encountered an aircraft maintenance culture that immediately worried him.

On his first day, Marino said, he heard a supervisor discussing with mechanics a colleague who had improperly signed off on a repair involving a valve that feeds air to the plane's air-conditioning system. The mechanic had not done the required operational check, Marino said, to ensure his fix worked, but signed off on the repair as if he had.

"Experience would have told you that is not what you do," Marino said. "If I were a manager, I would have fired him."

Also that first day, Marino said, he saw a mechanic who was supposed to be doing an aircraft familiarization exercise on a computer that is required by the Federal Aviation Administration. But he said he was stunned when he looked closely and saw the mechanic wasn't paying any attention to the exercise.

The man, Marino said, was playing a game on his iPhone.

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Marino's biggest complaint was the way Allegiant used what the FAA calls a "minimum equipment list," or MEL.

This is a list of parts or instruments that are allowed by the FAA to be inoperative during a flight. Aircraft can safely take off with some redundant systems or components down. An aircraft, for example, may have two autopilots, allowing one to be temporarily inoperative.

But this nonetheless erodes the safety margin, Marino said, and the FAA restricts how long a repair can be delayed.

The key to the MEL, Marino said, is that mechanics properly troubleshoot or diagnose a problem to confirm that a glitch experienced by the pilot in flight — like an autopilot shutting off at altitude — was actually caused by a specific piece of equipment being placed on the list, thus allowing the plane to fly.

If the work is done poorly and the wrong part is placed on the MEL, he said, then a plane will essentially be flying with an undiagnosed problem.

In one instance, Marino said, mechanics decided to put a ground spoiler, which helps an aircraft decelerate during landing, on the MEL. But he said they did not do a complete operational check to confirm the issue was fixed.

That, Marino said, would inevitably cause readings on cockpit instruments indicating a problem in the aircraft's next flight.

"Guess what happened when the aircraft took off." Marino said. "The pilot said we have to return to field. It was another return to field, another Allegiant norm that is accepted."

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John Goglia, a mechanic and crash investigator who served as a member of the National Transportation Safety Board, said the situation portrayed by Marino is highly plausible at an airline with a smaller fleet of aircraft like Allegiant, which operates about 80 aircraft. He does not know Marino.

"Allegiant has its airplanes on a very quick turnaround," Goglia said. "I guarantee to you it's happening. Quick turnarounds lend themselves to that kind of operation because mechanics don't have time to work on an airplane and take a delay. The guy on the other end of the phone (might say), 'Just put it on the MEL and get it out.' "

Goglia, however, said that sort of issue is not Allegiant's alone and might be true of other smaller carriers, as well. But he said that it is a serious safety issue and that the airline should be concerned with the large number of Allegiant flights that are forced to make emergency landings due to mechanical issues. In the industry, such events are called "often-returns."

Referring to five such landings the last week of December, Goglia said, "That many often-returns is amazing."

Allegiant said that MEL instructions are crafted by the FAA and the aircraft manufacturer, not the airline, and that it properly adheres to FAA rules governing how the list is used. The FAA allows some components to remain on the MEL for up to 10 days. Allegiant said its average is 1.7 days.

And information on MELs, the airline said, is reported to the FAA daily. The FAA said in a statement it has seen no "MEL discrepancies" at Allegiant for the last year, and the agency has not received reports of such problems.

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For Marino, one of the last straws was an aircraft at Sanford with an oil leak.

Marino said a mechanic doing a routine inspection of an aircraft two hours before its departure found a significant puddle of oil in the part of the engine known as a "tailpipe." He said he figured someone would be assigned to investigate.

Later, a pilot on the aircraft called to report he had found an oil puddle during his preflight walk-around. A lead mechanic, Marino said, either forgot the problem or chose to ignore it.

Oil leaks are not necessarily a safety threat. Marino said that in some circumstances, a small leak is permissible and need not ground a plane. Still, the leak must be investigated, he said, to ensure it won't endanger the aircraft. But for the pilot discovering it, Marino said, the aircraft would have taken off without that determination.

While this leak would not have endangered the aircraft, Marino said, it proved significant enough to temporarily ground it while the issue was dealt with.

"This is Allegiant's culture," he said. "We're going to do it the way we want in order to get the plane in the air. It's their uncomfortable norm."

The final straw came for Marino on his 10th day at work.

Marino said he was helping a mechanic deal with an autopilot that was switching itself off at altitude. But Marino said mechanics were replacing a display management computer that he knew could not be the cause of the problem. The computer, one of three on the aircraft, was not broken, Marino said.

As he worked, Marino discovered mechanics hadn't pulled a post-flight report from an aircraft diagnostic computer, which would help show the source of the autopilot malfunction.

He said he told a supervisor the DMC was not the source of the autopilot failure. But he said a supervisor insisted that he replace the DMC, though it was working properly.

Then, Marino said, the supervisor coerced him to falsely report in paperwork that the computer removed from the aircraft was, in fact, broken. Marino said he reluctantly did so. "I succumbed to the pressure," he said.

Though Marino said he still had enough time on his shift to repair the autopilot, supervisors made the decision to place it on the MEL, deferring a repair and allowing the airplane to fly. And again, he said, Allegiant hadn't followed proper MEL procedure before doing so.

Meanwhile, other mechanics working on the same aircraft had repaired a malfunctioning component in one of the plane's two air-conditioning systems. But Marino said they did not know how to do a complete operational check. Yet, they still signed off on the repair as if one had been done. Once again, he said, the problem was misdiagnosed.

The repair to the air-conditioning system could be critical because, if one were not operational and the second failed in flight, a pilot could be faced with a dangerous pressurization problem, Marino said.

"Even though they could not figure out how to test it, they decided it was going to be fine," said Marino, adding that this was a serious threat to safety. "But it is going to come right back on the lap of the flight crew."

Frustrated by a range of issues at Allegiant, Marino decided to quit on the ride home from work.

Emails show that Marino wanted to meet with Allegiant personnel to go over his concerns about the airline's safety culture. But he said Allegiant never took him up on the offer.

"I don't need this," he said. "I don't need the job. It is going to take a crash to get everybody's attention on this baloney. Allegiant has lost control of its product in house. Their maintenance is nothing short of obscene."

Times researcher John Martin contributed to this report. Contact William R. Levesque at levesque@tampabay.com. Follow @Times_Levesque.