Off-Duty Pilot Accused of Trying to Cut the Engines on an Alaska Airlines Flight

An off-duty pilot who was in a jump seat in the cockpit of an Alaska Airlines flight on Sunday was charged with more than 80 counts of attempted murder after he tried to cut fuel to the engines, prompting the plane to divert to Portland, Ore., the authorities said.

Flight 2059, operated by Horizon Airlines, an Alaska Airlines regional subsidiary, left Everett, Wash., around 5:23 p.m. and was headed to San Francisco when it reported “a credible security threat related to an off-duty Alaska Airlines pilot who was traveling in the flight deck jump seat,” Alaska Airlines said in a statement on Monday.

An airline spokeswoman said that the off-duty pilot tried to deploy the plane’s fire suppression system, which includes handles that, when pulled, close valves in the wings, shutting off fuel to the engines.

“After they are pulled, some residual fuel remains in the line, and the quick reaction of our crew to reset the handles restored fuel flow and prevented fuel starvation,” Alaska Airlines said.

One of the plane’s pilots told an air traffic controller that “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 issues in the back right now,” according to an audio recording posted on LiveATC.net, which shares live and archived recordings of air-traffic-control radio transmissions.

“I think he is subdued,” the pilot added.

The Port of Portland Police Department said in a statement that the flight crew “was able to detain the subject and the flight landed safely at Portland International Airport just before 6:30 p.m.”

The man was taken into custody without incident. The department identified him as Joseph D. Emerson.

According to the Multnomah County Sheriff’s Office, Mr. Emerson, 44, was booked into jail on Monday morning on more than 80 counts of attempted murder, a felony; more than 80 counts of reckless endangerment, a misdemeanor; and one count of endangering an aircraft, a felony.

Four crew members and 80 passengers were on the flight, Alaska Airlines said.

A passenger, Aubrey Gavello, told ABC News that after the man was taken off the plane, “the flight attendant got back on the speaker and said, plain and simple: ‘He had a mental breakdown. We needed to get him off the plane immediately.’”

Mr. Emerson, of Pleasant Hill, Calif., was scheduled to be arraigned on Tuesday, according to court records. It was not immediately clear if he had a lawyer. Messages left at a phone number listed under his name were not immediately answered on Monday, when sheriff’s office records indicated he was still in jail.

Michael Jernigan, who was a commercial airline captain for more than two decades before he retired from Alaska Airlines last year, said it was common practice for off-duty pilots to hitch a ride in the cockpit jump seat when shuttling to and from work.

He said he “never worried about it all.”

“Pilots behave themselves — they have a lot of money and time invested in their craft,” Mr. Jernigan said.

As a jump seat passenger, he said, he would stay quiet when the plane was below 10,000 feet. When it started cruising at higher altitudes, he said, he would often chat with the pilots, many of whom he got to know well over the years.

He said he could only speculate about what might have prompted an off-duty pilot to try to disrupt a flight. The episode, he said, was “very, very strange.”

The Air Line Pilots Association, a union that represents commercial airline pilots, commended “the quick and professional response of the two pilots and entire flight crew in securing the flight deck and landing the aircraft safely.”

“The safety of the flying public and our crews is at the foundation of everything we do, and we are fully cooperating with authorities as they investigate this incident,” the association said in a statement.

The union said that airline pilots in North America work in “one of the most highly vetted and scrutinized careers, and for good reason.”

Pilots in the United States, the union said, are evaluated throughout their careers through training, medical exams and other programs, and are subjected to random flight checks by the Federal Aviation Administration.

The F.B.I. in Portland said in a statement that no injuries were reported on the flight and that the agency, which is investigating, “can assure the traveling public there is no continuing threat.”

F.A.A. records indicate that Mr. Emerson received his airline transport pilot certificate, allowing him to serve as a captain on commercial airline flights, on July 10.

The F.A.A. said it was working with investigators and referred questions to the local authorities.

Pete Buttigieg, the transportation secretary, said in a statement on social media that he was grateful to the flight crew and air traffic controllers who “stepped up to guide this plane safely to Portland.” He said the F.A.A. would examine “any safety considerations for the future that emerge from investigations.”

Niraj Chokshi contributed reporting and Kirsten Noyes contributed research.