Video surveillance footage shows the Santa Clara teen shortly after 1 a.m. Sunday on the airfield, walking on the tarmac and near airplanes in fenced and guarded areas, according to a law enforcement official briefed on the investigation.
FBI Spokesman Tom Simon said the teen fell asleep in the plane before its 8 a.m. takeoff.
High altitude and low temperatures knocked him out during the 5 1/2-hour flight; he didn't regain consciousness until an hour after the plane landed in Hawaii, Simon said. Medical experts have said the boy may have survived the subzero temperatures and thin air of the plane's 38,000-foot cruising altitude because his body went into a hibernation-like state.
When the landing gear of a Boeing 767 retracts, there is little room to maneuver in the wheel well. The boy would have had to curl up in the fetal position or crouch down the entire time. And there is no way to get into the main cabin or luggage compartment without removing large pieces of the aircraft's interior, said Jon Day, general manager of Southern California Aviation, a maintenance yard in Victorville, Calif., that handles commercial jets.
The incident "raises serious concerns affecting passenger safety," said U.S. Rep. Eric Swalwell, D-Calif., who is asking the Government Accountability Office to assess airport perimeter safety nationwide.
The teen was resting in a hospital Tuesday and was set to return to San Jose. He was not expected to be charged with a crime.
The FAA says about one-quarter of the 105 stowaways who have sneaked aboard flights worldwide since 1947 have survived. Some wheel-well stowaways survived deadly cold and a lack of oxygen because their breathing, heart rate and brain activity slow down.
The Associated Press contributed to this report.