Fortunately, no passengers were believed to have been on board the Horizon Air Q400 when it was stolen from Seattle's Sea-Tac International Airport on Saturday afternoon (AEST).
The unidentified 29-year-old man spoke to a controller on a live air-traffic control feed during the hour-long episode.
Instead, the sheriff's office said the cause of the crash could have been either the pilot's inexperience, or his decision to pull mid-air stunts during his short flight.
Seattle-based The Air Current.com Editor-in-Chief Jon Ostrower said that "being able to power on and do a rudimentary preflight and engine start on a commercial airliner is not only the purview of trained airline pilots".
The Bombardier Dash-8 Q400 crashed into Ketron Island south of Tacoma, the sheriff's office said. A large plume of smoke is visible to residents surrounding Steilacoom, Washington.
"An airline employee conducted an unauthorised take-off without passengers at Sea-Tac", the statement said.
Footage shows pilot attempt the aerial maneuver after he hijacked the plane from Seattle-Tacoma International Airport in Washington state.
The sheriff said earlier that the man was a airline mechanic, but the airline said the employee was a ground service agent.More news: Canadian dollar falls after Saudi Arabia reportedly sells off assets
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And there was no indication that the incident was an act of terror, Pierce County Sheriff Paul Pastor told KIRO7 news station in Seattle.
In audio obtained from that conversation, the man - referred to as "Rich" in the transmission - is heard saying: "I've got a lot of people that care about me". (I'm) just a broken guy, got a few screws loose I guess.
He said he'd "like to apologize to each and every one of them".
According to the mercurynews.com, witnesses reported seeing the Bombardier Q400, a turboprop aircraft, perform a loop-the-loop and almost slam into Chambers Bay, all while being pursued by fighter jets.
The man, identified only as Rich, seems obviously manic and disturbed in the released audio as air traffic controllers attempt to guide him to safety.
"I'm not quite ready to bring it down just yet", the pilot says.
Horizon Air COO Constance von Muehlen said in a late-night video message "our hearts are with the family of the individual onboard as well as all our Alaska Air and Horizon Air employees". "Never really knew it until now". "I mean, I would hope it is, for a guy like me".
Witnesses at the airport, posting on social media, said they were told that someone had stolen an aircraft.
Billingsworth said he saw what appeared to be two jets following the plane.