A Sri Lankan man who was in a drug-induced psychosis when he threatened to set off a bomb on a plane he boarded at Melbourne Airport has had his sentenced reduced.

Manodh Marks was the first person in Australia to be sentenced for the offence of attempting to take control of an aircraft.

Marks was travelling to Sri Lanka via Kuala Lumpur in May 2017 when shortly after the flight took off, he retrieved a portable speaker and battery pack from his bag and falsely claimed it was a bomb.

He had used ice on the way to the airport, which induced the psychosis.

He told passengers on the Malaysia Airlines flight that he wanted to talk to the pilot.

"I have a bomb with me," he said.

Marks then ran to the cockpit door and announced that he "wanted to destroy the plane".

He was tackled to the ground by passengers, who used plastic cables to bind his hands and feet until they landed back at Melbourne Airport 15 minutes later.

He was sentenced in the County Court last year to 12 years in jail with a non-parole period of nine years.

Today, Victoria's Court of Appeal reduced his sentence to eight years in prison, with a non-parole period of five years.

Justices Simon Whelan, Karin Emerton and Robert Osborn found that the sentence imposed was "manifestly excessive" because the threat was a "trick" because the bomb was fake.

"There is no doubt that the judge was entirely correct when he observed that the effect of the applicant's conduct was just as terrifying for the passengers and crew as if he had had a real bomb, and the judge was entirely correct to take that matter into consideration when assessing the gravity of the offending," the justices said in their finding.

They said the means adopted to commit the offence must be a relevant consideration.

"It is of relevance that the applicant did not use actual force and that the purported bomb was not, in fact, a bomb or other device capable of causing harm to the plane or those travelling on it," the judgement said.

"To state the obvious, the applicant's offence would have to have been assessed as more grave had the bomb been real."

Justices Whelan, Emerton and Osborn said Marks's offending was not motivated by a financial, political or any other motive.

"The applicant had a delusional belief that he was acting in the best interests of those on board the plane," they said.

"He believed he was acting to save them."

They also took into account Marks' guilty plea, his contrition and his prospects of rehabilitation.

Marks will have to serve five years in prison before he can apply for parole.

He has already served 890 days in pre-sentence detention. (ABC News)