Air traffic controllers, civilian and commercial pilots and even two F-16 fighter jets were dispatched to contact a Michigan pilot as he flew cross country in 2015, only to helplessly watch as his plane plunged into the Atlantic.

Transcripts released by the NTSB last week reveal a harrowing two hours and 34 minutes in which controllers from Minneapolis to Washington, as well as nearby pilots and military jets, tried in vain to contact Dr. Michael Moir, a Gaylord dentist who was en route to an airplane safety seminar in Atlantic City.

The cause of the Sept. 10 crash remains a mystery two years later, although clues in the report issued Sept. 25 suggest hypoxia, a debilitating loss of oxygen that slows motor skills, confusion and loss of consciousness, afflicted the aviator before his fatal nosedive.

Moir’s final two confirmed transmissions to controllers, just after leaving Gaylord, were slightly flawed. When he contacted the Minneapolis Air Route Traffic Control Center, which guides planes in northern Michigan, he said he was at 11,000 feet — then quickly corrected it to 17,600 feet — before controllers instructed him to go to 25,000 feet.

Moir repeated the instruction, referencing the altitude. And, as also is customary for pilots, he ended his transmission using the phonetic alphabet for last letters of his plane’s tail number, which was N370MM.

“(Cleared) to 2-5-0 mike-mike,” he repeated.

Moir’s plane was equipped to fly at high altitudes. The single-engine Mooney had an oxygen system, the use of which is recommended for flights at or above 10,000 feet. Without it, a pilot would draw less oxygen with each breath at high altitudes, and risk being overcome by hypoxia. Moir also brought a pulse oximeter, a finger-mounted device that tracks pulse and oxygen levels in the blood.

Moir was flying over Lake Huron at about 260 mph. Just 13 minutes after he was cleared to climb to 25,000 feet, a Minneapolis controller asked Moir to contact Toronto on a different radio frequency for continued air traffic, a pattern that would ordinarily repeat itself as he flew in and out of different radar coverage sectors.

“Mooney zero-mike-mike, contact Toronto Center on 132.57. Good day,” she said.

There was no answer.

Four more times she tried to reach Moir, then called a Delta Airlines commercial jet in Moir’s vicinity in hopes of relaying the message in case his radio reception was poor.

“Could you broadcast for a Mooney 370 mike-mike, November 370 mike-mike, and have him go to Toronto on (radio frequency) 132.57?”

The Delta pilot tried unsuccessfully three times before the controller enlisted another plane, an on-demand jet service called XOJET, whose pilot tried two more times.

“Maybe he got it for you, but we did not get a response,” the pilot reported at 1:09 p.m., about 55 minutes after Moir’s last confirmed transmission.

Moir’s Mooney had already traversed Lake Huron and most of southern Ontario on course for Atlantic City. It was hurtling at 265 mph and about to head over Lake Erie.

Loss of oxygen, loss of judgment

Hypoxia can be deceiving. As the body loses oxygen, among the first signs is a loss of judgment as the brain is impaired. But symptoms vary for different people.

In the first stage of hypoxia, you don’t notice anything, said Dr. Gregory Pinnell, founder and flight surgeon for Air Docs, a Saginaw-based aviation medicine practice. That’s followed by a compensatory stage, in which the pulse quickens and respiration deepens, signs that can be picked up by close monitoring of a pulse oximeter like the one Moir had on board.

“Eventually you get to the disturbance phase, where you know you’re in trouble, but you just really don’t care,” Pinnell said. In the final, critical stage, “you’re a victim and can only be helped.”

The loss of oxygen often leads to feelings of euphoria and indifference.

Age and health also play a factor. Moir was 68. An antihistamine was found in his system, which could have made him more susceptible to hypoxia. The symptoms he was treating could also have impacted him.

“A cold, sniffles or flu-like symptoms can impact altitude tolerance,” Pinnell said.

Nevertheless, a pilot has three to five minutes of useful consciousness without supplemental oxygen at 25,000 feet above sea level, according to the Pilot’s Handbook of Aeronautical Knowledge.

‘He’s going into the ocean’

Soon after Moir crossed Lake Erie, New York controllers assumed responsibility for the plane, which had been designated as “nordo,” shorthand for flying without radio contact.

“They might scramble fighters on him soon, just to let you know,” a New York traffic controller told a colleague at 2:07 p.m., after the plane passed Williamsport, Pa.

Controllers decided first to try to reach Moir on a “guard” frequency monitored by pilots and reserved for in-flight emergencies, so they enlisted other airport controllers and pilots in his vicinity to call out on that channel.

By this time, numerous aircraft were calling out for zero-mike-mike. When the plane was 20 miles northwest of Allentown, Pa., the tower controller made an attempt and, according to the transcript, heard a breakthrough.

A pilot confirmed the radio frequency and signed off with zero-mike-mike, Moir’s call sign.

Zero-mike-mike “should be coming over to you, New York,” the controller reported.

But Moir never called New York. Controllers asked Allentown to try again.

“Yeah, he’s not listening to me this time,” the controller replied.

New York called an Allentown supervisor, trying to confirm the controller’s report.

“He’s sure on the call sign? It was 3-7-0 mike-mike?”

“Yeah, because I walked in and caught the tail end of that bit,” the supervisor said.

By this time, 2:19 p.m., Moir was just west of the Philadelphia suburbs, flying at about 255 mph. He was entering the sensitive airspace of controllers in Washington, D.C., who for the next 25 minutes repeatedly tried to reach him.

Five miles north of Atlantic City, at 2:38 p.m., the plane made its first significant change. It began descending.

The Atlantic City tower reported that two F-16s, with the call sign Cosmic 4-1, were rolling to intercept the flight. It had already descended to 2,700 feet.

“Cosmic 4-1, radar contact,” Atlantic City controllers told the F-16s. “He’s just at 800 feet. He’s going into the ocean.”

Less than a minute later Atlantic City reported “mooney zero-mike-mike radar contact lost” and the rescue crews discovered signs of the wreckage.

Cause of death

Moir’s autopsy revealed little beyond the fact that the impact caused his death. The antihistamine in his blood was at a therapeutic level, but likely something he was used to, said Pinnell, the flight doctor. His wife told the FAA that he used it for hay fever.

The one significant finding came from the post-crash wreckage, pulled from 45 feet below the surface of the Atlantic.

“An elbow fitting that was connected to the oxygen regulator assembly, which connected an oxygen line to the tank, was found loose,” the NTSB report says. “The fitting could be moved in both directions by hand without resistance.”

The NTSB will probably release a likely cause of the accident within a few weeks.

Regardless of the outcome, Pinnell recommends high-altitude training for pilots — so they know their symptoms for hypoxia — like that which he leads at Western Michigan University.

“Any pilot flying at altitude should go in a lab to get an idea what their signs are so you can respond,” he said. “If you get hypoxic, you’ve got to do something, you have to respond affirmatively in a practiced manner, or you’re going to have a bad day.”

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