Authorities believe an American teenager found dazed and disoriented on the apron of Kahului airport in Maui survived a flight across the Pacific from California, stowed away inside the wheel well of a Hawaiian Airlines jet.

The story told by the so-far unidentified 16-year-old, who was released into state child-services care after being given the all-clear by doctors, is perplexing experts who argue that surviving the five-hour, 30-minute journey at altitudes of up to 38,000 feet - higher than Mount Everest - would seem humanly impossible.

Yet the FBI said yesterday that video footage showed him walking across the tarmac at the international airport in San Jose, south of San Francisco, early on Sunday towards the Boeing 767 wide-bodied plane before it took off for the Hawaiian island. The FBI added that Maui airport had security footage of the boy crawling out of the main port-side wheel-well.

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Special Agent Tom Simon said the aircraft was on the ground for almost an hour when "dumbfounded" ground staff spotted the boy near the belly of the jet and approached him to ask who he was.

"The boy later claimed that he had run away after a family argument and hopped [over] the fence at the San Jose airport to reach the plane but had no recollection of the flight itself," said Mr Simon. "It's a miracle. It's amazing he survived."

The agent suggested that the teenager had been unconscious for "the lion's share of the flight" but there was no shortage of sceptics last night.

"This is a first in medical science and a first in physiology, someone surviving at 35,000ft or higher for five hours with no supplementary oxygen," John Nance, an aviation consultant, told ABC News yesterday

He noted that, apart from the lack of oxygen at such an altitude, the temperature would have dropped to -62C. "I don't believe the kid was in the wheel well - that's what it comes down to," he insisted.

The US Federal Aviation Administration (FAA), however, said that there had been cases of people surviving such ordeals because their bodies went into a kind of enforced hibernation.

Last August, a stowaway survived a domestic flight in Nigeria in a wheel well but it was much shorter and at a lower altitude.

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After a stowaway fell out of the wheel well of a British Airways flight from Angola and plunged into a street in East Sheen, near Heathrow, in 2010, a pathologist testified that he believed the man may have been still alive when he fell, or at least until quite soon before.

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While temperatures in the wheel well would have plummeted as the plane headed west to Hawaii, the FAA also suggested that the cold may have been moderated very slightly in the wheel well by stored heat in the tyres after they retracted, as well as from hydraulic lines in the area.

While the boy has not been charged with any crime in Hawaii, the FBI said it would investigate how he managed to penetrate the secure tarmac area at San Jose airport and climb into the Boeing without being detected.

Eric Swalwell, a member of Congress for California who sits on the Homeland Security Committee, said in a Twitter posting: "I have long been concerned about security at our airport perimeters. Stowaway teen demonstrates vulnerabilities that need to be addressed."

Police in San Jose said last night that they were looking at whether to file criminal charges against the boy.

Hawaiian Airlines said: "Our primary concern now is for the well-being of the boy, who is exceptionally lucky to have survived."

Investigators say the boy fled his home in Santa Clara, California after a family argument. Security cameras caught him jumping over an airport fence and clambering into the undercarriage of the passenger jet.

Aviation expert Peter Forman told Hawaii News Now that the chances of surviving such conditions are "very remote".

'The odds of a person surviving that long of a flight at that altitude are very remote", he said.

"A lot of people would only have useful consciousness for a minute or two at that altitude. For somebody to survive multiple hours with that lack of oxygen and that cold is just miraculous. I've never heard of anything like that before".

A spokesman for the FBI confirmed that the boy will not face criminal charges, and has been referred to child protective services.

California stowaway amazes doctors in Hawaii after five-hour flight