Portland, Oregon - An off-duty US pilot who tried to shut down the engines of a commercial passenger plane in mid-flight has been indicted on 84 counts, prosecutors said Tuesday.

Joseph Emerson said he had taken magic mushrooms and thought he was having a nervous breakdown when he lunged for handles that would have starved the engines of fuel during an October flight from the state of Washington to California.

Emerson, who told police he had not slept in 40 hours, also tried to open an emergency exit in the rear of the aircraft and had to be restrained by the cabin crew during an emergency landing, according to court documents released earlier.

A grand jury in Oregon, where the Alaska Airlines plane made an emergency landing, indicted Emerson on 83 counts of recklessly endangering another person – one for each person on the October 22 flight – and one count of endangering an aircraft, Multnomah County District Attorney Mike Schmidt said.

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There were no charges for attempted murder.

Emerson is set to appear in court on December 7.

Emerson (44) had boarded the flight – which was operated by Horizon Air – between Everett, Washington, and San Francisco, sitting in the jump seat of the cockpit, in line with airline policy for non-working staff.

A short way into the journey, after chatting with the pilots "Emerson attempted to grab and pull two red fire handles that would have activated the plane's emergency fire suppression system and cut off fuel to its engines," the Justice Department said at the time.

"After a brief physical struggle with the pilots, Emerson exited the cockpit."

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He was arrested after the emergency landing.

In an interview from the jail where he was being held, the pilot told the New York Times he had not intended to hurt anyone, but had pulled the handles in an effort to jolt himself from a hallucinogenic state that began when he took mushrooms two days earlier.

"I pulled both emergency shutoff handles because I thought I was dreaming and I just want to wake up," Emerson told investigating police, according to a criminal complaint.