An off-duty pilot attempted to shut off the engines in flight, Alaska Airlines says

An Alaska Airlines flight was forced to make an unexpected landing Sunday night after an off-duty pilot who was riding in the cockpit allegedly attempted to disable the aircraft's engines.

"I'll just give you a heads-up. We've got the guy that tried to shut the engines down out of the cockpit," one of the pilots said to air traffic controllers in audio posted by LiveATC.net. "It doesn't seem like he's causing any issue at the back. I think he's subdued."

The flight, which was operated by Horizon Airlines, took off from Everett, Wash. around 5 pm Sunday evening. The Embraer 175 jet had to be diverted from San Francisco to Portland, Ore. where it landed safely.

In a statement, Alaska Airlines described the incident as "a credible security threat related to an off-duty Alaska Airlines pilot who was traveling in the flight deck jump seat."

"The jump seat occupant unsuccessfully attempted to disrupt the operation of the engines," according to the statement, before "the crew secured the aircraft without incident. "

It's routine for off-duty pilots, flight attendants and other airline staff to catch a ride in the jump seat behind the pilot and first officer.

The off-duty pilot was arrested after the plane landed at Portland International Airport. Authorities there have identified him as Joseph David Emerson. He's now facing 83 counts of attempted murder, among other charges, including reckless endangerment and endangering an aircraft.

The Federal Aviation Administration said it is supporting law enforcement investigations into the incident.

"All passengers on board were able to travel on a later flight," Alaska Airlines said. "We are grateful for the professional handling of the situation by the Horizon flight crew and appreciate our guests' calm and patience throughout this event."

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