PORTLAND (US): An off-duty pilot riding in the extra seat in the cockpit of a Horizon Air passenger jet tried to shut down the engines in midflight and had to be subdued by the crew, according to a pilot flying the plane.

Authorities in Oregon identified the man as Joseph David Emerson, 44. He was being held Monday on 83 counts each of attempted murder and reckless endangerment and one count of endangering an aircraft, according to the Multnomah County Sheriff’s Office.

The San Francisco-bound flight on Sunday diverted to Portland, Oregon, where it was met by officers from the Port of Portland, who took Emerson into custody.

Seattle-based Alaska Airlines, which owns Horizon, a regional carrier, did not name Emerson, but said on Monday that the threat was posed by one of its pilot who was off duty but authorised to occupy the cockpit jump seat.

The airline said the captain and co-pilot reacted quickly, “engine power was not lost and the crew secured the aircraft without incident.” Alaska said in a statement that no weapons were involved.

One of the pilots told air traffic controllers that the man who posed the threat had been removed from the cockpit.

“We’ve got the guy that tried to shut the engines down out of the cockpit. And he — doesn’t sound like he’s causing any issue in the back right now, and I think he’s subdued,” one of the pilots said on audio captured by LiveATC.net. “Other than that, we want law enforcement as soon as we get on the ground and parked.”

FAA records indicate that Emerson has a valid license to fly airline planes.

Sunday’s incident occurred on a 76-seat Horizon Air Embraer 175 that left Everett, Washington, at 5:23 p.m. local time and landed in Portland an hour later.

Alaska said passengers continued on to San Francisco on a later flight.