Off-duty pilot accused of trying to crash Alaska Airlines jet, before being subdued

An off-duty pilot riding as a passenger in the cockpit of an Alaska Airlines flight Sunday tried to seize control of the plane headed from Seattle to San Francisco, forcing the flight to divert to Portland, Oregon, according to the airline and a source familiar with the matter.

A pilot assigned to the flight told air traffic controllers a person riding in the cockpit of flight 2059 attempted to turn off the aircraft's engines in flight. Pilots will occasionally ride a cockpit "jump seat" when traveling in an official capacity or commuting to another airport.

Joseph Emerson, 44, has been arrested by the Port of Portland Police Department and charged with 83 felony counts of attempted murder, 83 counts of reckless endangerment and one count of endangering an aircraft, online booking records show.

Emerson is the off-duty pilot who is accused of trying to seize control of the flight, a source familiar with the matter told CNN. The airline Emerson works for wasn't immediately known.

The plane took off from Seattle Paine Field International Airport and was diverted to Portland International Airport because of the "credible security threat," the airline said in a statement Monday.

"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 issues in the back right now," the pilot told Seattle-area air traffic controllers, according to audio recorded by "I think he's subdued. Other than that, we want law enforcement as soon as we get on the ground and are parked."

The Alaska Airlines crew "reported a credible security threat related to an authorized occupant in the flight deck jump seat," the airline's statement said.

"Following appropriate FAA procedures and guidance from air traffic control, the flight safely diverted to Portland International Airport," Alaska Airlines said. The flight was operated by Horizon Air, a regional carrier owned by Alaska Airlines. "The event is being investigated by law enforcement authorities."

The FAA told CNN it is aware of the incident and supporting a local law enforcement investigation.

CNN has reached out to local and federal authorities for further information.