SAN JOSE, Calif.

- A 15-year-old boy found his way onto an airport's 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 boy, who lives in Santa Clara, Calif., hopped out of the left rear wheel well of a Boeing 767 on the Maui airport tarmac Sunday, according to the FBI. 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 climbed into the left rear wheel well of the first plane he saw in San Jose.

"He got very lucky that he got to go to Maui but he was not targeting Maui as a destination," Simon said.

He passed out in the air and didn't regain consciousness until an hour after the plane landed in Hawaii, Simon said. When he came to, he climbed out of the wheel well and was immediately seen by airport personnel, who escorted him inside where he was interviewed by the FBI, Simon said.

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 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.

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

San Jose International Airport spokeswoman Rosemary Barnes says airport employees monitor security video feeds from throughout the 1,050-acre airport around the clock. However, she said 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 onto the tarmac during the night, "under the cover of darkness," Barnes said.

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 ongoing investigation.

Hawaiian Airlines spokeswoman Alison Croyle said airline personnel noticed the boy on the ramp after the flight arrived and immediately notified airport security.

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

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, Simon said.

The city of San Jose, which owns and operates the California airport, is not planning on pursuing criminal charges against the teen based on the current information available.

The FAA says 105 stowaways have sneaked aboard 94 flights worldwide since 1947, and about 1 out of 4 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.