OLYMPIA, Wash. — Investigators are piecing together how an airline ground agent working his regular shift stole an empty Horizon Air turboprop plane, took off from Sea-Tac International Airport and fatally crashed into a small island in the Puget Sound.
Officials said Saturday the man was a 3½-year Horizon employee and had clearance to be among aircraft, but that to their knowledge, he wasn’t a licensed pilot.
Richard B. Russell, 29, used a pushback tractor to maneuver the aircraft so he could board and then take off Friday evening, authorities said.
It is unclear how he attained the skills to do loops in the aircraft before crashing about an hour after taking off into a small island in the Puget Sound, authorities said.
Before it went down, the plane was chased by military jets that were scrambled to intercept the aircraft.
One of the military jets deployed is part of the fleet for the 104th Fighter Wing at Barnes Air National Guard Base in Westfield, Mass., said Lieutenant Colonel John Keeler, the unit’s chief of staff.
The F-15C jet is on loan to the 142nd Fighter Wing from the Portland Air National Guard Base in Oregon, which deployed the fighters, he said. The pilot who flew the jet based at Barnes is assigned to the 142nd Fighter Wing, according to Keeler.
The turboprop plane crashed nearly an hour after it was taken from a maintenance area, though officials said it did not appear that the fighter jets were involved in the crash of the aircraft. In a news release issued Saturday, the North American Aerospace Defense Command said the F-15C aircraft did not fire on the plane.
At a news conference in Seattle-Tacoma International Airport, officials from Alaska Airlines and Horizon Air said that they are still working closely with authorities as they investigate what happened.
‘‘Safety is our No. 1 goal,’’ said Brad Tilden, CEO of Alaska Airlines. ‘‘Last night’s event is going to push us to learn what we can from this tragedy so that we can ensure this does not happen again at Alaska Air Group or at any other airline.’’
The bizarre incident points to one of the biggest potential perils for commercial air travel: airline or airport employees doing harm.
‘‘The greatest threat we have to aviation is the insider threat,’’ said Erroll Southers, a former FBI agent and transportation security expert. ‘‘Here we have an employee who was vetted to the level to have access to the aircraft and had a skill set proficient enough to take off.’’
Seattle FBI agent in charge Jay Tabb Jr. cautioned that the investigation would take a lot of time, and details, including the employee’s name, would not be released right away.
There was no connection to terrorism, said Ed Troyer, a spokesman for the sheriff’s department.
Video showed the Horizon Air Q400 doing large loops and other dangerous maneuvers as the sun set on Puget Sound. There were no passengers aboard.
Ground service employees direct planes for takeoff and gate approach, de-ice them, and handle baggage.
Southers said Russell could have caused mass destruction. ‘‘If he had the skill set to do loops with a plane like this, he certainly had the capacity to fly it into a building and kill people on the ground,’’ he said.
Gary Beck, CEO of Horizon Air, said it wasn’t clear how the man knew to start the engine, which requires a series of switches and levers.
The plane crashed on tiny Ketron Island, southwest of Tacoma, Wash. Video showed flames amid trees on the island, which is sparsely populated and accessible only by ferry. No structures on the ground were damaged, Alaska Airlines said.
Sheriff’s department officials said they were working to conduct a background investigation on the Pierce County resident.
The aircraft was stolen about 8 p.m. Alaska Airlines said it was in a ‘‘maintenance position’’ and not scheduled for a passenger flight. Horizon Air is part of Alaska Air Group and flies shorter routes throughout the US West. The Q400 is a turboprop aircraft with 76 seats.
Russell could be heard on audio recordings telling air traffic controllers that he is ‘‘just a broken guy.’’ An air traffic controller called the man ‘‘Rich,’’ and tried to persuade him to land the airplane at Joint Base Lewis-McChord.
‘‘Oh, man. Those guys will rough me up if I try and land there,’’Russell responded, later adding ‘‘This is probably jail time for life, huh?’’
Later Russell said: ‘‘I’ve got a lot of people that care about me. It’s going to disappoint them to hear that I did this. . . . Just a broken guy — got a few screws loose, I guess.’’
Flights out of Sea-Tac, the largest commercial airport in the Pacific Northwest, were temporarily grounded during the drama.
Investigators expect to be able to recover both the cockpit voice recorder and the event data recorder from the plane.
Laura Crimaldi of the Globe staff contributed to this report.