Before the jet's pilots nearly lost control of their plane as it hurtled down a Las Vegas runway, it flew for weeks with a problem that could have killed everyone on board.
It never should have happened, according to a report by the Federal Aviation Administration inspector who reviewed the August 2015 incident.
AAR Aircraft Services, part of North America's largest aviation maintenance company, had improperly recorded its work, skipped maintenance steps and bungled critical inspections on the Allegiant Air plane, he found.
"Every stop gap in place to enhance safety to a critical flight control was skipped, bypassed or improperly done," the inspector, Carlos Flores, wrote in the FAA's official report on the incident.
Flores recommended that the FAA fine AAR the maximum amount it could, to prevent "potential tragedies" in the future.
FAA managers reviewed the investigation and decided to handle the situation differently.
They didn't fine the company.
They didn't demand any additional changes at AAR, even though one acknowledged Flores' belief that "the conditions that created the safety risk originally" hadn't changed.
They didn't assign anyone to investigate further.
Instead, they wrote AAR a "letter of correction" and signed off on the fixes it had already put in place.
Then they closed the case, and told the public the problem had been solved, a Tampa Bay Times review of the FAA's full investigative file shows.
AAR continues to be a major maintenance contractor for Allegiant and other large airlines.
Today, FAA officials say they made the right call. FAA spokesman Ian Gregor said in a statement that "inspectors and managers from several offices in the FAA safety oversight division agreed that AAR Aircraft Services took the appropriate actions to correct the root cause of the incident."
But two former FAA officials who reviewed the full investigation at the Times' request said Flores' findings were alarming and should have triggered a larger investigation into AAR.
"It's really disturbing from a safety perspective," said Loretta Alkalay, an aviation attorney who spent 30 years as a regional counsel prosecuting enforcement cases for the FAA.
AAR spokeswoman Kathleen Cantillon said it "is fully compliant with FAA requirements."
"AAR's first priority is safety of flight," she said in a statement. "We have worked closely with Allegiant and the FAA to take corrective actions."
Gregor said the agency "thoroughly reviewed" AAR's procedures when it performed a "wide-ranging review of Allegiant's operations" in spring 2016.
"The FAA and Allegiant continue to closely monitor AAR's operations," he said.
Allegiant Air, which operates the vast majority of flights at St. Pete-Clearwater International Airport, declined to comment.
The FAA never intended for the full results of its investigation to become public.
Last year, the Times published an investigation showing Allegiant's planes were four times as likely to fail during flight as those operated by other major U.S. airlines, and another that focused on FAA's lax oversight of Allegiant.
The Times first requested the FAA's investigative file while reporting those stories. The FAA provided a version of the report that was heavily redacted, hiding Flores' concern that the Las Vegas incident was a symptom of a dangerous, ongoing problem.
The Times appealed. The FAA responded last week and declined to release most of the redacted information.
But along with its response, the agency accidentally sent the Times the entire unredacted report.
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On August 17, 2015, Allegiant Flight 436 rolled down a Las Vegas runway. As the plane picked up speed, its nose started rising, even as the pilots pushed the yoke all the way down. At about 138 miles per hour, the captain aborted the takeoff and the plane screeched to a halt.
When Allegiant mechanics inspected the plane, it was clear what had gone wrong.
A nut had slipped off the rod that connects the plane's controls to its elevators — flaps on the plane's tail that controls its pitch. A cotter pin on the rod should have kept the nut in place, but there was no evidence it had been installed when the plane went in for maintenance at an AAR repair facility in Oklahoma City three months before.
If the plane had made it off the ground — or the nut had slipped off in flight — the pilots would have lost control in the air.
The FAA assigned Flores, one of its senior inspectors overseeing Allegiant, to lead the investigation.
About six months later, the FAA said that employees at AAR working on the Allegiant plane had missed steps and improperly documented their work when installing one of the elevators.
But AAR had made changes since the incident, the FAA said. Where two inspectors had failed to notice the botched maintenance, the company added a third inspector. Workers would only be allowed to work on critical parts of the plane after watching a safety video.
The fixes were "appropriate and sufficient to prevent future violations of this nature," Gregor said.
The heavily redacted investigation detailed several mistakes by mechanics at AAR, but didn't detail systemic issues.
But underneath the blackouts, the report said the FAA's investigator did not believe AAR's changes would keep the problem from happening again.
A thorough audit of the plane's paperwork by Allegiant could have caught the problem, Flores wrote.
But he singled out AAR's employees for "egregious complacent behavior" that led to the incident.
Mechanics didn't fill out required maintenance logs, and technicians either skipped inspections or did them so superficially it defeated the point of the inspections altogether.
He chronicled five separate times AAR employees should have caught the flaw before the plane left the station. But over and over, required paperwork proving the maintenance had been done was missing.
It added up to "careless (and possibly reckless) conduct" by AAR, he wrote — "deliberate and systemic acts of noncompliance" with Allegiant's maintenance procedures and federal aviation rules.
"They are clearly a repeat offender that show an unwillingness to admit errors unless it will not cost the company money," he wrote.
• • •
Government watchdogs have been warning for years that the FAA's oversight of repair stations like the one in Oklahoma City is lacking.
In 2013, the Department of Transportation's Office of Inspector General released an audit that said the agency wasn't catching and fixing serious problems at repair stations. In one case it cited, an FAA inspector noted the same infraction at the same repair station three years in a row, but accepted the same fix for the problem all three times.
U.S. airlines are only becoming more dependent on outsourced maintenance, an industry that the watchdog office estimated had more than tripled in less than two decades.
According to AAR's spokeswoman, the company "has performed over 24 million man hours of maintenance work on aircraft for dozens of airlines" over the last five years.
The station in Oklahoma City works on 17 air carriers, including Alaska Air. In Indianapolis an AAR station does maintenance on Delta Air Lines' jets. And before U.S. Airways merged with American, it sent planes to AAR's station in Miami.
AAR's parent company also pulls in billions of dollars of federal taxpayer money for services that include aircraft maintenance, aircraft leasing and airlift services. In September, less than a year after the FAA finalized its investigation, it won a $10 billion, 11.5 year contract to maintain the fleet of aircraft the State Department uses to combat international narcotics trafficking.
• • •
Flores submitted his report in November 2015. It landed on the desk of David Ibarra, a technical specialist based out of the FAA's regional office in Van Nuys, Calif. He was responsible for recommending the agency's next course of action.
He acknowledged Flores' concerns, but recommended against fining the company.
Ibarra's decision relied on the agency's "new compliance philosophy," which the FAA introduced in 2015. It encourages airlines and their employees to report safety problems by punishing them less harshly after mistakes.
"Our evolved approach to oversight does not suggest that we are going easy on compliance," the FAA's website says about the policy. "However, FAA will not use enforcement as the first tool in the toolbox."
This was not, however, the first time these issues had come up at AAR.
In 2014, another Allegiant plane went in for service at an AAR repair station. But a day after it was returned to Allegiant, its right engine flooded with fuel on takeoff, causing it to rev uncontrollably. The pilot had to shut it down and make an emergency landing back at the airport.
The investigation into that incident concluded an AAR mechanic had skipped maintenance steps, and neither Allegiant nor AAR's inspectors noticed before the plane returned to service.
After the Las Vegas incident, Flores noted that AAR "had two very similar situations that risked lives and property within a one year period, only to find the corrective action by the repair station had no effect."
The FAA declined to answer questions about its decision to not sanction AAR. Flores declined to comment.
But former FAA inspector Mary Rose Diefenderfer said the FAA should have fined the company, based on its own policies, and that the agency could have gone as far as revoking its certificate to operate.
AAR "should have been at least temporarily shut down while an FAA white-glove team came in to investigate," she said. "That would have occurred if blood had been shed, but it's the FAA way not to be proactive."
Contact Nathaniel Lash at email@example.com Follow @Nat_Lash.