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.