A Sri Lankan man was jailed for 12 years on Thursday for threatening to detonate a bomb on an international flight out of Melbourne, striking fear into more than 200 passengers and crew.

Manodh Marks, 26, forced Malaysia Airlines flight MH128, bound for Kuala Lumpur, to turn back soon after take-off in May 2017 after screaming that he had a bomb.

The agitated, drug-affected Marks ran down the aisle of the Airbus A330 holding two electronic devices with flashing blue lights, saying he was going to blow up the plane.

He was actually holding a speaker device and a power bank.

AAP

"You ran to the galley outside the pilot's door and you announced there that you had a bomb and you wanted to destroy the plane," Victoria County Court Judge Michael McInerney said.

"The passengers and crew were not only concerned but convinced that you were indeed in possession of a bomb.

"One can imagine the fear and distress of everyone on board."

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Judge McInerney said the bomb threat happened during the crucial take-off period, distracting the captain and putting those on board at increased risk.

"I believe the passengers were placed in danger," he said.

The captain had to make a mayday call to air traffic control and turn the plane around after a crew member gave the hijacking code "Romeo Romeo".

Marks was eventually overpowered by passengers and restrained with cable ties as the flight returned to Melbourne Airport.

90 minutes of terror

Police made passengers stay on the plane for almost 90 minutes before storming the aircraft and arresting Marks, AAP reports.

Officers copped criticism for taking so long to free the passengers, who still believed the device could be a bomb, placing luggage around it in case it exploded.

One passenger said the events of the flight were etched in his memory and he was now sensitive to sudden movements.

"Yes, there was a moment where I feared for my life," the passenger said in a statement.

Marks pleaded guilty to the federal charge of attempting to take control of an aircraft, which carries a maximum penalty of 20 years in jail.

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The Sri Lankan had been living in the Melbourne suburb of Dandenong and studying hospitality. But he had fallen into regular ice use, and on the night of the flight was suffering a drug-induced psychosis with delusions.

It was not suggested the bomb threat was pre-planned or that Marks had any terror-related goals.

Marks told doctors that in his psychotic state he believed the plane was going to crash and wanted to turn it around.

Earlier on the day of the bomb threat he had been released from a psychiatric facility for drug issues but he took ice on his way to the airport.

Judge McInerney said Marks would return to his native Sri Lanka after serving his sentence and must spend at least nine years behind bars before being eligible for parole.