SAN JOSE, Calif. — For all the tens of billions of dollars that the nation has spent on screening passengers and their bags, few airports made a comparable investment to secure the airplanes themselves.

As the case of the San Jose stowaway shows, it did not take a sophisticated plan for a 15-year-old boy to spend about seven hours in what is supposed to be a secure area of Silicon Valley’s main airport — much of it in a wheel well of the jet that took the teen to Hawaii.

Aviation security experts say San Jose International is hardly alone when it comes to weaknesses in securing its airfield. While some larger airports have in recent years invested heavily in technology that can detect intruders, others have systems that sound too many false alarms — or don’t provide enough useful information in the first place.

“I don’t think San Jose is different than 80 percent of the airports around the country” in how secure its perimeter is, said Rafi Ron, former head of security at the closely guarded airport in Tel Aviv, Israel.

Like other major airports, San Jose has dozens of security cameras that survey its restricted areas. Indeed, cameras recorded the boy on the tarmac, but no one noticed until hours later — after he had survived the 5½-hour flight and clambered onto the tarmac on the island of Maui.

“What happened in San Jose can happen as we speak at other airports, because nobody can watch all these monitors” that feed video from around the airport, said Ron.

San Jose does not, evidently, have more sophisticated technology that can detect someone climbing a perimeter fence, track a trespasser with radar or automatically alert authorities at a central post when a video camera picks up potentially suspicious activity.

These “intrusion detection systems” are the best security available, though they are not foolproof. In 2012, a man whose personal watercraft ran out of fuel swam to the edge of New York’s Kennedy Airport, scaled a fence and walked about 2 miles along the airfield before being spotted.

All this despite a $100 million system of surveillance cameras and motion detectors.

The boy told authorities he jumped a fence in San Jose and climbed up the landing gear of the closest plane. Video shows him on the airfield a little after 1 a.m. Sunday, said a law enforcement official briefed on the investigation. The official was not authorized to speak publicly about the case and spoke on the condition of anonymity.

It is not clear how the teen spent all the time before the plane took off around 8 a.m.