US airport chiefs have launched a major security probe after a 15-year-old boy climbed into a airliner's wheel well, then flew for five freezing hours from California to Hawaii.
The boy, who lives in Santa Clara, California, hopped out of the left rear wheel well of a Boeing 767 on the Maui airport tarmac on Sunday, according to the FBI.
Authorities found the schoolboy wandering the airport grounds with no identification. He was questioned by the FBI and taken by ambulance to hospital, where he was miraculously found to be unharmed.
In Honolulu, FBI spokesman Tom Simon said the teenager climbed into the wheel well of the first plane he saw at San Jose International Airport.
"He got very lucky that he got to go to Maui, but he was not targeting Maui as a destination," Mr Simon said.
He passed out in the air and did not regain consciousness until an hour after the plane landed in Hawaii. When he came to, he climbed out of the wheel well and was immediately seen by airport staff who escorted him inside where he was interviewed by the FBI, Mr Simon said.
It was not immediately clear how the boy stayed alive in the unpressurised space, where temperatures at cruising altitude can fall well below zero and the air is too thin for humans to stay conscious. A Federal Aviation Administration study of stowaways found that some survive by going into a hibernation-like state.
Authorities are now trying to determine how the boy slipped through multiple layers of security, including wide-ranging video surveillance, German shepherd dogs and Segway-riding police officers.
San Jose Airport spokeswoman Rosemary Barnes said airport staff monitored security video feeds from throughout the 1,050-acre airport round the clock. But no one noticed images of an unidentified person walking on the airport ramp and approaching Hawaiian Airlines Flight 45 in the dark until security agents reviewed the footage after the plane had landed in Hawaii and the boy had been found.
The airport, in the heart of Silicon Valley, is surrounded by fences, although some sections do not have barbed wire and could easily be scaled.
The boy found his way on to the tarmac during the night, "under the cover of darkness", Ms Barnes said.
Hours later, surveillance video at Kahului Airport showed the boy getting out of the wheel well after landing, said Hawaii's Department of Transportation.
Hawaiian Airlines spokeswoman Alison Croyle said airline staff noticed the boy on the ramp after the flight arrived and immediately called airport security.
"Our primary concern now is for the well-being of the boy, who is exceptionally lucky to have survived," she said.
Isaac Yeffet, a former head of security for Israeli airline El Al who now runs his own firm, Yeffet Security Consultants, said the breach showed US airport security still had weaknesses.
"Shame on us for doing such a terrible job," he said. "Perimeters are not well protected. We see it again and again."
And a congressman who serves on the Homeland Security committee wondered how the boy could have sneaked on to the airfield unnoticed.
"I have long been concerned about security at our airport perimeters. #Stowaway teen demonstrates vulnerabilities that need to be addressed," tweeted Eric Swalwell, a Democrat who represents the San Francisco Bay Area's eastern cities and suburbs.
Unlike checkpoint security inside the airport, which is overseen by the Transportation Security Administration, airport perimeters are policed by local authorities, as well as federal law enforcement.
Airport police were working with the FBI and the TSA to review security.
The boy was released to child-protective services in Hawaii and not charged with a crime, Mr Simon said. The city of San Jose, which owns and operates the California airport, is not planning to pursue criminal charges against the teenager.
The FAA says 105 stowaways have sneaked aboard 94 flights worldwide since 1947, and about one out of four survived. But agency studies say the actual numbers are probably higher, as some survivors may have escaped unnoticed and bodies could fall into the ocean undetected.
In August, a 13 or 14-year-old boy in Nigeria survived a 35-minute trip in the wheel well of a domestic flight after stowing away. Authorities credited the flight's short duration and its altitude of about 25,000 feet. Others who hid in wheel wells have died, including a 16-year-old killed aboard a flight from Charlotte, North Carolina, to Boston in 2010 and a man who fell on to a London street as a flight from Angola began its descent in 2012.
An FAA review of high-altitude wheel well survivors said they typically clamber past the main landing gear into a wing recess area next to where the gear retracts. On some aircraft, that space is large enough for two small adults.