The 16-year-old boy who survived a flight across the Pacific Ocean stowed away in an airplane's wheel well has everyone wondering just how he achieved this remarkable feat.

The teenager climbed aboard Hawaiian Airlines Flight 45 at San Jose International Airport Sunday morning (April 20) and survived the five-and-a-half-hour flight to Maui with minimal oxygen at an altitude of 38,000 feet (11,600 meters) and temperatures of about minus 80 degrees Fahrenheit (minus 62 degrees Celsius). The boy remained unconscious for most of the flight, but was unharmed, The Associated Press reported.

The teenager probably survived by entering a state of suspended animation, in which the body's metabolism slows down and requires less oxygen and energy, medical experts say. [Infographic: The Limits of Human Survival]

"It is a true miracle that a lot of physicians have postulated in the past," said Dr. Evelina Grayver, a cardiologist at North Shore University Hospital in Manhasset, N.Y.

The boy most likely lost consciousness due to the low oxygen level as the plane ascended, and then, the low temperatures probably put his cells into a frozen state, Grayver told Live Science.

Not everyone believes the story, however. "Somebody surviving at 35,000 feet for five hours with no supplemental oxygen supply; I just don’t believe it," aviation consultant Jim Nance told ABC News.

Human hibernation?

There have been rare cases of people going into states of suspended animation in extreme cold.

In 2006, a 35-year-old man survived 24 days on a snowy mountainside in Japan. His body temperature had plummeted to 71 F (22 C), his organs had shut down and his metabolism had slowed to a crawl, yet he recovered fully from the incident.

In the case of the boy on the airplane, Grayver suspects the symbiotic relationship between low oxygen and low temperatures brought the metabolic processes of the boy's cells to a halt.

"When an organism suspends its biological processes, it cannot do anything wrong," Grayver said.

As the plane descended to land, the cells would have rewarmed gradually and started functioning normally again, she said.

The boy's young age likely also played a role in his miraculous survival. He probably didn't have heart disease or congenital heart defects that could have caused fatal heart arrhythmias, Grayver said. 

Therapeutic hypothermia

Doctors routinely cool down a patient's body temperature during treatment for various conditions. "Therapeutic hypothermia" slows down the metabolism in order to reduce the risk of tissue damage during cardiac arrest, stroke, brain or spinal cord injury, fever after brain trauma or newborn oxygen deprivation.

The procedure involves cooling the body to near-freezing temperatures for extended periods of time. But the boy on the airplane was also deprived of oxygen.

"The symbiotic relationship between low oxygen and low temperatures one day may be developed into an improved technique to extend the shelf life of human organs," Grayver said.

This teenage-stowaway case and others like it raise questions about the reversibility of the suspended-animation state. For instance, Grayer said, for how long can humans be frozen or deprived of oxygen?"

A medical examination revealed the boy had not suffered lasting harm. If he had brain injury from oxygen deprivation, it would be evident by now, Grayver said. Similarly, heart failure or arrhythmias (irregular heart rhythms) would show up within the first 24 to 48 hours. "He's incredibly lucky," she said.

This is not the first time someone has apparently survived by stowing away on an airplane. A teenage boy in Nigeria survived in the wheel well of a plane during a 35-minute flight at an altitude of about 25,000 feet (7,600 m), according to the AP. Other wheel-well stowaways have not been so lucky, the news agency said.

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This story was originally written for LiveScience and has been republished with permission here. Copyright 2014 LiveScience, a TechMediaNetwork company.