The US Federal Bureau of Investigation has concluded that former Horizon Air staffer Richard Russell, acting alone, stole and intentionally crashed a Horizon Bombardier Q400 in August
The FBI found that Russell "piloted the aircraft and that the final descent to the ground was intentional," says the agency in an investigation summary. "Extensive investigative activity failed to reveal any additional subjects involved in the planning or execution of the unauthorised flight."
The FBI, however, found no motive.
"Although investigators received information regarding Russell’s background, possible stressors and personal life, no element provided a clear motivation for Russell’s actions," it says.
Russell stole the Q400 (registration N449QX) from a cargo area at Seattle Tacoma International airport on 10 August, according to officials.
He took off without clearance on a 73min flight during which he reportedly performed aerobatic manoeuvres before crashing on an island in Puget Sound. Russell died in the crash, the FBI says.
The Q400's flight data recorder "indicated significant sideslip on the airplane during the final minute of flight, but the airplane appears to have remained in control, and the final descent to the ground appears to have been intentional", says the FBI.
"If the pilot had wanted to avoid impact with the ground he had time and energy to pull the column back, raise the nose and initiate a climb," it adds.
Instead, the control column remained in a forward position until 6s prior to the crash.