Aviation and security experts were at a loss Monday to explain how a 16-year-old boy from Santa Clara managed to scale a fence at Mineta San Jose International Airport before surviving a five-hour flight to Maui in the wheel well of a Hawaiian Airlines jet. After the plane landed at Kahului Airport in Maui at 10:30 a.m. local time, he remained unconscious for about an hour before emerging from the wheel well, said FBI Special Agent Tom Simon in Honolulu. "Hawaiian Airlines personnel in Maui noticed the individual on the ramp" and immediately notified airport security, said Hawaiian Airlines spokeswoman Alison Croyle. San Jose airport spokeswoman Rosemary Barnes said the airport, the FBI and Transportation Security Administration officials were reviewing security measures and remain "concerned about the health and welfare of the teenager." "Despite this, no system is 100 percent, and it is possible to scale an airport perimeter fence line, especially under cover of darkness, and remain undetected, and it appears this is what this teenager did," Barnes said. A study of wheel well stowaways by the Federal Aviation Administration noted, It is also likely that various unsuccessful attempts were never documented (or known), the bodies falling into an ocean, or into a remote land area.