Shortly after he stole an airplane from his employer, Horizon Air ground service agent Richard Russell barreled down a runway, took off and flew the two-engine turboprop above the Puget Sound, flying in dramatic loops before crashing in a wooded area of a nearby island.

Russell died in Friday night's crash.

Airline executives said they aren't sure whether the 29-year-old, who was hired by the Alaska Air Group's regional arm Horizon Air in February 2015, had formal flight training.

Russell didn't appear to have a pilot's license, Horizon Air CEO Gary Beck said in news conference over the weekend. The grounds crew worker told air traffic control agents that he played some video games.

"There were some maneuvers that were done that were incredible maneuvers," Beck said. "I don't know how he achieved the experience that he did."

Beck said "commercial aircraft are complex machines" and not as easy to fly as a small plane such as a Cessna 150. Alaska Air CEO Brad Tilden said the airline did not know if Russell had any training.

The incident at Seattle-Tacoma International Airport has exposed blind spots in aviation security and safety, and challenges in screening employees and addressing potential mental health problems. The National Transportation Safety Board is reviewing the cockpit voice recorder and flight data recorder from the wreckage, which will provide more insight into what happened.

Russell was part of a team of ground service workers whose duties included loading and unloading baggage, tidying planes and towing. He used a tractor to move the 76-seat Q400 turboprop plane 180 degrees before taxiing to the runway, when an air traffic controller repeatedly asked him to identify himself.