SEATTLE (AP) — Three passengers sued Alaska Airlines on Thursday, saying they suffered emotional distress from an incident last month in which an off-duty pilot is accused of trying to shut down the engines of a plane while catching a ride in the cockpit from Washington state to San Francisco.

In the complaint filed Thursday in King County Superior Court in Washington state, San Francisco residents Matthew Doland and Theresa Stelter and Paul Stephen of Kenmore, Washington, alleged that the pilot should never have been allowed in the cockpit because he was suffering from depression and a lack of sleep.

Alaska Airlines said in an emailed statement that it is reviewing the complaint. "The pilots and flight attendants operating Flight 2059 responded without hesitation to ensure the safety of all onboard," it added. "We are incredibly proud and grateful for their skilled actions."

Alaska pilot Joseph David Emerson, 44, was riding in the jump seat — an extra seat in the cockpit — when he suddenly said "I'm not OK" and tried to pull two handles that would engage a fire-suppression system and cut fuel to the engines, authorities said in charging documents.

Flight 2059, operated by Alaska affiliate Horizon Air, diverted safely to Portland, Oregon, after the pilots quickly subdued Emerson and he was voluntarily handcuffed in the back of the plane, police said.

The lawsuit said the plane experienced "what felt like a nose-dive," though some passengers quoted in news accounts have not described any such thing. Passenger Aubrey Gavello told ABC News: "We didn't know anything was happening until the flight attendant got on the loudspeaker and made an announcement that there was an emergency situation and the plane needed to land immediately."

According to the complaint, the plaintiffs have suffered from anxiety, insomnia, fear of flying and other emotional effects as a result of the incident. The lawsuit seeks class-action status on behalf of other passengers and says the airline owed the highest duty of care to its passengers and failed to follow that when it allowed Emerson in the cockpit.

"Airlines can and should take simple and reasonable steps before each flight to challenge the presumption that every pilot who shows up at the gate is rested, sober, and in the right state of mind to fly," Daniel Laurence, aviation lawyer at The Stritmatter Firm, which is representing the plaintiffs, said in a statement. "Emerson's statements while in the air and shortly after his arrest show that had the airlines here done so, he would never have been allowed aboard. ... Only luck prevented it from becoming a mass disaster."

It is a common practice for off-duty pilots to catch rides in jump seats, and in some rare emergencies they have pitched in to help, even saving lives.

Emerson has pleaded not guilty to attempted murder charges in Oregon state court and faces arraignment later this month on a federal charge of interfering with a flight crew.