A US pilot who tried to shut off a passenger plane's engines mid-flight will serve no additional prison time, a federal court has ruled.

The judge sentenced Joseph Emerson to credit for time served and supervised release for three years at a hearing in Portland, Oregon.

"Pilots are not perfect. They are human," Judge Amy Baggio said. "They are people and all people need help sometimes."

Emerson was off-duty at the time of October 2023 flight, and blamed his behaviour on a mental breakdown caused by hallucinogenic mushrooms. He had pleaded guilty in September to a single federal charge of interfering with a flight crew.

The former Alaska Airlines pilot had already pleaded no contest to state charges of endangering an aircraft and 83 counts of endangering another person. For those charges he received five years of probation and 50 days in jail.

The deal with federal prosecutors allowed him to avoid a sentence of up to 20 years behind bars.

Before the sentencing was announced, Emerson spoke and said he regretted the harm he caused to society.

"I'm not a victim. I am here as a direct result of my actions," he told the court, according to the Associated Press. "I can tell you that this very tragic event has forced me to grow as an individual."

He hugged his lawyers and shared a tearful embrace with his wife after the judge announced his sentence, the AP reported.

The flight on 22 October, 2023 was on its way from Everett, Washington, to San Francisco, California, with 80 passengers aboard. It was then diverted to Portland, Oregon.

One pilot cited in the criminal complaint said he had to wrestle with Emerson until he stopped resisting. The entire incident lasted about 90 seconds.

After being subdued, Emerson said to flight attendants: "You need to cuff me right now or it's going to be bad" and later tried to reach for the emergency exit handle during the plane's descent.

One flight attendant told investigators they had observed Emerson saying "I messed everything up" and that he "tried to kill everybody".

Emerson had argued that that the drugs made him unaware of his actions at the time, that he had been grieving the death of a friend, and that he did not intend to harm passengers.

He added that he had not slept for about 40 hours before the flight, and felt that he needed to "wake up".

"I had no intention of crashing an actual airplane," Emerson, 46, told CBS News in an interview. "I wanted to wake up."

Lawyers for Emerson had argued that no prison time was warranted because he had been "already adequately punished".

He lost his licence to fly after his arrest, and is now working part-time as a pressure washer, according to The Oregonian newspaper.

He has also paid $60,000 (?46,000) in restitution, and is also visiting schools to become a substance abuse counsellor.

He and his wife have also started the group Clear Skies Ahead, which intends to bring attention to mental health struggles among pilots. (BBC)

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