How did the teen stowaway survive in plane’s wheel well?

WATCH ABOVE: Experts say a 16-year-old stowaway, on a flight to Hawaii, should never have survived the flight. Shirlee Engel reports.

Investigators are calling it a “miracle”: a 15-year-old boy emerged from the wheel well of an airplane after a five-hour journey from San Jose to Maui.

He defied freezing temperatures, lack of oxygen and lack of pressure without any protection. Baffled doctors aren’t sure how the teen survived the hours-long flight.

For starters, passengers on board sit in a pressurized cabin. The lack of pressure outside is a deadly hazard.

READ MORE: Teen stowaway survives flight to Hawaii in plane’s wheel well

“We are talking about pressures at nearly 40,000 feet. That’s going to be 30 per cent less than the pressure at the top of Mount Everest. And keep in mind that a lot of people don’t survive on Mount Everest even with extraordinary conditioning,” Roger Connor told NBC News. Connor is the curator at the National Air and Space Museum.

Without pressure and oxygen, hypoxia could set in. Think of a scuba diver descending and ascending too quickly: “At high altitudes your body succumbs to hypoxia. It doesn’t get the oxygen it needs to survive and most people would pass out and die within a few minutes,” Dr. Richard Besser told ABC News.

Hypoxia, in short, is an oxygen shortage. In order to function properly, your body needs a certain level of oxygen circulating in the blood to cells and tissues. Once this oxygen level drops, you’ll encounter a shortness of breath, according to the Mayo Clinic.

Then there’s the fear of hypothermia. In that case, your body loses heat faster than it can produce it. Normal body temperature usually sits at about 37 C. When it drops, your heart, nervous system and other organs can’t work correctly.

When mild hypothermia sets in, the stowaway will begin to shiver. When the person’s core temperature falls from 35.5 C to 34 C, he or she may begin to shiver violently and experience symptoms similar to hypoxia, with slurred speech and irrational behaviour. But when our core temperature falls to between 33 and 30 C, it becomes impossible to maintain the proper internal temperature.

An early study on airline stowaways found that at 2,440 metres, there is a slight increase in breathing and the oxygen level in the blood decreases from 97 per cent to 92 per cent. At 4,575 metres, the reaction time of a person decreases by as much as 50 per cent.

By the time the plane climbs to 5,490 metres, the rate of breathing decreases to 65 per cent to compensate for the lack of oxygen. At this point, visual and cognitive symptoms of hypoxia set in.

By 6,710 metres it becomes almost impossible to remain conscious as the oxygen in the blood that flows to the cells has fallen to 50 per cent.

Officials are guessing that the temperatures outside this particular flight probably dipped to below -40 C.

Under that trifecta of circumstances – low oxygen, extreme cold, lack of pressure – it’s very likely the boy was unconscious for most of the trip, Peter Hackett, director of the Institute for Altitude Medicine, told the Washington Post.

“The body temperatures drops and that cools the brain, and neuronal activity is suppressed. So the brain shuts down – it goes into what is almost like hibernation, without causing irreparable damage. And then when it warms up, you can be normal,” Hackett told the newspaper.

Hibernating animals do the same – in some cases their breathing and heart beat slow to a couple of times per minute, doctors told ABC News.

Hackett said that the teen was probably breathing only five per cent oxygen at 30,000 feet – a steep dip from the 21 per cent his body is accustomed to.

Maybe it wasn’t that cold in the wheel well, Dr. Howard Mell told USA Today. That way, he wouldn’t have frozen to death.

“I’m not saying he couldn’t have done it because apparently he could,” Mell said. U.S. Federal Aviation Administration research suggests that warm hydraulic fluid lines could have helped to provide heat but it’d be snuffed out as the plane ascended.

Then there are the logistics: if you don’t fall to your death by the 200-mile-per-hour winds, you could get crushed by the landing gear, the LA Times reports.

FAA statistics suggest that the boy’s feat is a rarity. Since 1996, there have been 105 stowaways on 94 flights worldwide – more than 76 per cent of the time, they ended in deaths.

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