Smoke rises from the site on Ketron Island near Seattle where a Horizon Air turboprop plane crashed Friday after it was stolen from Seattle-Tacoma International Airport.
Friday’s theft of a Horizon Air passenger plane from Seattle-Tacoma International Airport exposed the aviation vulnerabilities that persist even after efforts to enhance security following the Sept. 11, 2001, terrorist attacks.
Many questions about the incident—in which an airline employee took off with the plane and then crashed on a sparsely populated island in the Puget Sound—remain unanswered. But experts say it will prompt a rethink of how to secure aircraft at airports.
The employee, a man who had worked at Horizon Air for 3½ years, was a ground-service agent and, according to airline officials, didn’t have a pilot’s license.
Alaska Air Group
Horizon Air’s parent company, will examine what if anything needs to be changed, Alaska Chief Executive Brad Tilden said at a press conference Saturday: “It’s far too early to say what additional procedures we might implement.”
Before the crash, the man flying the plane pulled off “incredible maneuvers,” said Horizon Air CEO Gary Beck. Air-traffic controllers were tracking the man’s stunts above the Seattle metropolitan area as they tried to get him to land the plan away from populated areas.
Airliners generally don’t have locks on their doors or require keys to start. While there are procedures to secure aircraft, Mr. Tilden said the U.S. aviation industry generally focuses on securing airfields and then authorizes employees with proper credentials to work there.
“This is an airline, internal-security issue,” said Jeff Price, a consultant on aviation security. “We need to get out of the traditional aviation-security mind-set, where we think that more screening and more surveillance and more cops will solve this problem.”
The Horizon Air employee, who local authorities say died, was part of a team whose duties include towing aircraft and was authorized to be in the area where the Bombardier Q400 with 76 seats was parked.
Most airlines have rules about how planes should be stored overnight, but industry officials say they can vary from carrier to carrier. Typically, the doors are supposed to be secured. If parked near a gate, the passenger bridges are supposed to be moved away from the aircraft. The wheels on flight-ready plans should also be locked, experts say.
When planes are parked overnight—at or near maintenance areas—caterers, mechanics and cleaning crews have routine access. They know how to open doors, if necessary.
But to fly a plane, someone would have to know and follow a complicated sequence of tasks that include fueling, starting engines and programming the flight computer.
“The doors to airplanes are not keyed like a car,” Mr. Tilden said. “There’s not an ignition key like there would be on a car.”
In some cases, airline employees can have special training and authorization to move aircraft around the airport, said a former senior New York City airport official. These employees, while not pilots, have limited ability to operate aircraft controls as they are pulled by small vehicles around airport grounds.
Since the Sept. 11 terrorist attacks, airlines, federal security officials and law-enforcement agencies have focused attention and spent tens of billions of dollars plugging gaping holes in aviation security.
At airports large and small, there has been an emphasis on installing enhanced fencing and deploying more-advanced motion detectors and other sensors to identify intruders.
Likewise, security experts in the U.S. and other countries have publicly warned about dangers posed by members of terrorist groups or “lone wolf” attackers posing as airline or airport employees. The result has been more-rigorous employee screening, tighter control of worker-identification badges, stepped-up checks of access points and more frequent drills to test and verify those systems.
Airport-security experts say co-workers are an important line of defense. Airlines should have anonymous reporting systems that can potentially flag unusual behavior to management, said Mr. Price.
Aviation-security officials have increasingly become worried about insider threats.
This risk was tragically highlighted more than three years ago when
a 27-year-old Germanwings co-pilot, deliberately crashed a jetliner, killing all 150 people onboard. Lubitz had been treated for suicidal tendencies ahead of the crash but had hidden his conditions from the airline. European aviation-safety officials last month adopted pilot mental-health rules in response.
In the U.S., regulators and carriers cooperate on voluntary reporting programs designed to prompt employees who are having mental or substance-abuse problems to seek help. Other workers also are encouraged to let management know about such difficulties confronting fellow employees.
In February 2016, one person died in the suspected bombing of an Airbus SE A321 plane departing Mogadishu, for which Islamic State claimed responsibility. Somali officials said the bomber was aided by two people dressed as airport workers.
The Pentagon, Department of Homeland Security and the Federal Aviation Administration have meanwhile fine-tuned procedures to coordinate and scramble jet fighters to investigate and potentially prevent hostile acts by hijacked planes
The North American Aerospace Defense Command said it has conducted about 1,800 intercepts of civilian aircraft since September 2001. Only a tiny percentage of those missions involved airliners. Those cases typically involved pilots who failed to maintain radio contact with controllers. The vast majority of the intercepts were triggered by private pilots who got lost, disoriented or flew into restricted airspace.
In Friday’s incident, the military scrambled two F-15 jets to intercept the rogue plane.
—Jay Greene contributed to this article.