SAN JOSE, Calif. - A 16-year-old boy scrambled over an airport fence, crossed a tarmac, and climbed into a jetliner's wheel well, then flew for five freezing hours to Hawaii - a misadventure that forced authorities to take a hard look at the security system that protects the nation's airline fleet.

The teenager, who lives in Santa Clara, Calif., hopped out of the wheel well of a Boeing 767 on the Maui airport tarmac Sunday. Authorities found the high school student wandering the airport grounds with no identification. He was questioned by the FBI and taken by ambulance to a hospital, where he was found to be unharmed.

FBI spokesman Tom Simon in Honolulu said the teen did not remember the flight from San Jose.

It was not immediately clear how the boy stayed alive in the unpressurized space, where temperatures at cruising altitude can fall well below zero and where the air is too thin for humans to stay conscious. An FAA study of stowaways found that some survive by going into a hibernationlike state.

On Monday, authorities tried to determine how the boy slipped through multiple layers of security, including wide-ranging video surveillance, German shepherds, and Segway-riding police officers.

Security footage from the San Jose airport verified that the boy climbed a fence and crossed a runway Sunday morning to get to Hawaiian Airlines Flight 45, Simon said.

That airport, in the heart of Silicon Valley, is surrounded by fences, although many sections do not have barbed wire and could easily be scaled.

The boy climbed over during the night, "under the cover of darkness," San Jose airport spokeswoman Rosemary Barnes said Monday.

Hours later, surveillance video at Kahului Airport showed the boy getting out of the wheel well after landing, according to a statement from Hawaii's Department of Transportation. The video was not released because of the continuing investigation.

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, Simon said.

San Jose police said they would forward the findings of their investigation to the district attorney, who would decide whether to file criminal charges in California.

The FAA says that 105 stowaways have sneaked aboard 94 flights worldwide since 1947 and that 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.