The first sign something was off was when the ground crew at Kahului Airport in Maui noticed a boy wandering the tarmac, dazed and confused. The story he told officials was even more incredible.
He told authorities he was from Santa Clara, California, and ran away from home Sunday morning, said FBI Special Agent Tom Simon. He didn't have an ID and was carrying only a comb.
The 16-year-old apparently hitched a ride from San Jose, California, to Maui, Hawaii, in the landing-gear wheel well of a Boeing 767, Hawaiian Airlines said.
He hopped an airport fence, ran to the plane and climbed onto Hawaii Airlines Flight 45, the FBI said. Once confident that the teen did not present a threat, the FBI dropped out of the investigation.
"It appears that this teenager scaled a section of our perimeter," Mineta San Jose International Airport spokeswoman Rosemary Barnes told CNN. The boy "was able to proceed onto our ramp under cover of darkness and enter the wheel well of an aircraft."
Officials for the city of San Jose, California, which operates the airport, are not planning any legal action, a spokeswoman for the city, Rosemary Barnes, said Monday.
Hawaiian Airlines said, "Our primary concern now is for the well-being of the boy, who is exceptionally lucky to have survived."
He certainly is. As unlikely as it sounds, officials believe the boy rode in the tiny, cramped compartment for almost five hours, at altitudes that reached 38,000 feet, without oxygen and under subzero temperatures.
"It sounds really incredible," said aviation expert Jeff Wise. "Being in a wheel well is like all of a sudden being on top of Mount Everest."
Between the oxygen depletion and the cold, life expectancy "is measured in minutes," Wise said.
The boy is in the custody of child welfare services workers in Hawaii, said Kayla Rosenfeld, a spokeswoman for the state's Department of Human Services. She said Monday afternoon that officials have notified the boy's family that he is safe.
A rare club of survivors
But some people have survived. Since 1947, 105 people are known to have attempted to fly inside wheel wells on 94 flights worldwide, the Federal Aviation Administration's Civil Aerospace Medical Institute says. Of those, 25 made it through, including a 9-year-old child -- a survival rate of 24%. One of the flights went as high as 39,000 feet.
The conditions can put stowaways in a virtual "hibernative" state, the FAA says.
Someone could slip into unconsciousness so that the body cools and "the central nervous system is preserved," said CNN aviation expert Michael Kay. Also, he said, "there could be a situation where inside the bay is warmer than the external air temperature and you wouldn't get the instantaneous freezing of the skin."
Still, "for somebody to survive multiple hours with that lack of oxygen and that cold is just miraculous," airline analyst Peter Forman told CNN affiliate KHON in Honolulu.
The boy's survival is "dumb luck mostly," says Dr. Kenneth Stahl, trauma surgeon at Miami's Jackson Memorial Hospital. The temperature outside the airplane could have been as low as 75 or 80 degrees below zero, said Stahl, who is also a pilot. "Those are astronomically low temperatures to survive."
The boy was likely so cold that "he was essentially in a state of suspended animation," Stahl said. Being young likely worked in his favor, too. "No adult would have survived that," Stahl added.
The boy could face permanent brain damage from the experience -- in fact, it's "more likely than not," Stahl said. He could face neurological issues, memory problems or a lower IQ.
The teen also could have a kidney injury because when the body freezes, particles of muscle enter the blood stream and damage the kidneys, Stahl said. He could also lose tissue due to frostbite.
Videos bear out events
Surveillance camera footage shows the boy hopping the fence at Mineta San Jose International Airport, the FBI said.. There's also camera footage of him walking across the ramp in San Jose toward the Hawaiian aircraft, the airport said.
Video "is under review by federal and local law enforcement officials here," said airport spokeswoman Barnes. "And we'll continue to review that to determine where, in fact, the teenager was able to scale the fence line."
The boy told investigators he crawled into the wheel well of the plane and lost consciousness when the plane took off.