A 3 ½ year employee of Horizon Air had specialized training and security clearance, helping him carry out his plan to steal a Horizon Air passenger jet from its parking spot at Sea-Tac Airport on Friday evening.

“He worked his shift yesterday. We believe he was in uniform. His job is to be around airplanes,” said Brad Tilden, CEO of Horizon’s parent company Alaska Airlines.

Richard Russell, 29, flew the plane for over an hour before it crashed on Ketron Island in south Puget Sound. There were no other people on board, and the man piloting the plane has not been recovered.

WATCH: Who is Richard Russell

Airline officials said the ground service agent had a certification to tow aircraft, which results in a higher clearance than other ground agents.

Authorities say Russell used a tow vehicle in the airport’s Cargo 1 area to turn around a Q400 prop plane 180 degrees and prepare it for take-off.

Former co-workers, who asked not to be named, described Russell as "super nice and super chill."

One colleague said, "People did not see him as a threat."

According to his blog, the 29-year-old grew up in Alaska, met his wife in Oregon, and moved to Sumner, Washington three years ago. That's when he got a job at Horizon Air as a ground service agent, a job that allowed him to travel.

LISTEN: Cockpit audio from worker who stole empty plane from Sea-Tac Airport

"Most importantly I get to visit those I love most," Russell said in a video he produced on YouTube.

Airline and airport officials would not say during a briefing to reporters Saturday exactly when airport staff determined the plane was in the process of being stolen. They said they wanted to review video recordings, which are called tower tapes, to determine the plane’s precise movements during taxing and takeoff.

Authorities are still piecing together how Russell gained a working knowledge of the cockpit and flight procedures. They also seemed to marvel at his stunt flying once airborne.

“To my knowledge, he didn’t have a pilot’s license,” said Horizon CEO Gary Beck.

Beck said flying the “complex machine” would be more difficult than a private plane.

“I don’t know how he achieved the experience he did,” Beck said.

WATCH: Stolen plane flies erratically over Puget Sound

The FBI’s special agent in charge of the Seattle office, Jay S. Tabb, said up to 40 FBI agents were working the case overnight.

When asked about Russell’s mental condition Tabb replied, “It’s too early to comment on that.”

WATCH: Aerials of crash scene on Ketron Island

An FBI official said they were in touch with the deceased employee’s family last night after the crash.

More coverage of the stolen plane crash:

Horizon Air employee stole, crashed plane on Pierce County island

How did man who stole plane at Sea-Tac fly it for over an hour?

Friendly tone contradicted drastic actions of Seattle plane thief

FBI recovers man's body and black box from wreckage of stolen plane

Childhood friend believes man who stole plane had brain trauma from football

Firefighters battle more than flames after Ketron Island plane crash