Even though an airport employee stole a plane and flew it for an hour before crashing, a Port of Seattle official said "all security protocols were handled appropriately" at Seattle-Tacoma International Airport.
Commissioner Courtney Gregoire said the employee, Richard Russell, had a security badge, and that all employees are subject to background checks.
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She said the Friday night incident was a "one-in-a-million experience."
But she also said the airport, often known as Sea-Tac, will work on possible security improvements.
"Our airport director, our head of security (and) our airport operations team have been on the phone with lots of airports," Gregoire told reporters Monday.
"We'll be working through some of those associations nationally and internationally."
Human remains found
On Sunday, investigators found human remains in the wreckage of the stolen Horizon Air plane.
The remains are almost certainly those of 29-year-old Russell, from Sumner, Washington. But the FBI is waiting for confirmation from the local medical examiner's office.
Russell was the only person aboard, the Pierce County Sheriff's Department said. The Sheriff's Department described Russell as suicidal but did not elaborate.
Authorities said Russell took off in the stolen plane at Seattle-Tacoma International Airport, flew for about an hour with military jets chasing him and crashed the 76-seater on a heavily wooded island.
The flight data recorder and components of the cockpit voice recorder have been recovered and are with the National Transportation Safety Board, according to the FBI.
The Horizon Air plane is unrecognizable, said a NTSB official. The plane went through several 100-foot-high lines of trees and was fragmented from the crash into pieces tiny enough to pick up, NTSB Western Pacific Region chief Debra Eckrote said Sunday.
"You couldn't even tell it was a plane except for some of the bigger sections, like the wing section," Eckrote said. "Even the small sections, most of it doesn't resemble a plane."
The flight data recorder is burned but intact, Eckrote said, and will be shipped tomorrow. It is expected to arrive in Washington, D.C., on Tuesday, she said. Analysis will begin midweek. It is unknown when the full analysis will be completed.
'A complete shock' to the family
The plane crash has left Russell's family devastated.
In a statement, his family said his "intent was not to harm anyone," referring to audio recordings of Russell talking to air traffic control during the flight.
"This is a complete shock to us," the family said Saturday night. "We are devastated by these events, and Jesus is truly the only one holding this family together right now."
Russell had worked as a Horizon Air ground service agent for 3½ years. His job included directing aircraft for takeoff and gate approach, handling baggage and tidying and de-icing planes.
Russell, or "Beebo" as some called him, was "a faithful husband, a loving son and a good friend," his family said. They also said he was "kind and gentle to each person he met."
Officials don't believe Russell had a pilot's license, and they don't know how he knew to fly the plane. Jeremy Kaelin said he worked with Russell in 2016, and remembered "happy, funny" chats with him in the break room.
"He was a nice guy," Kaelin said. "He was definitely one of the harder working people on the ramps."
Military jets did not bring the plane down
Russell had worked a shift Friday when he took a plane parked in a maintenance area of the airport, said Brad Tilden, CEO of Alaska Air Group, which owns Horizon Air.
He used a vehicle known as a pushback tractor to move the empty turboprop plane and took off without authorization at 7:32 p.m. Friday, officials said.
Russell flew for about an hour, talking periodically with air traffic controllers and making turns and even some aerobatic maneuvers as two armed F-15 jets followed him, officials said.
Video from a witness on the ground shows the plane at one point pulling up for a loop, putting the aircraft upside-down and then pulling back up just feet above a body of water.
The plane eventually crashed on sparsely populated Ketron Island, starting a fire in the woods and killing Russell. No one outside the plane was injured, officials said.
The cause of the crash wasn't immediately known, but authorities said the F-15s did not bring the plane down.
The FBI said it does not consider the incident terror-related but the theft of a commercial aircraft from a major US airport has exposed a gap in airline security.
Authorities will try to piece together how a security scare of this magnitude occurred at a major airport.
Experts said the crash exposed alarming holes in airport security, and is likely to prompt a major review of industry security measures.
"This is going to be a major learning event for the industry," CNN aviation analyst Justin Green said. "This is a really big deal."
Russell managed to steal the Horizon Air turboprop from a maintenance area by himself. He was in uniform, had proper credentials and had clearance to be in secure aircraft areas, said Tilden, the airline CEO.
"They're credential employees. They're there to work on the airplanes. ... This is aviation in America. The doors of the airplanes are not keyed like a car. There is not an ignition key like a car. The setup in aviation in America is we secure the airfield," Tilden said.
Russell appeared to have broken protocol several times. He shouldn't have been able to board the plane alone and go unnoticed. He also moved the plane by himself while protocol calls for two people to tow an aircraft.
"The fact he was out there by himself, towing the aircraft by himself ... then moving the tracker out of the way, so he could get on the aircraft and move. The fact that all of that happened without even being noticed by anyone on the ground service crew, that is just phenomenal to me," said CNN analyst and former FAA safety inspector David Soucie.