A Sri Lankan national who allegedly threated to bomb a Malaysian Airlines flight from Melbourne has a history of psychiatric illness and fears for his safety in custody, his lawyer has told a court.

Manodh Marks, 25, who is in Australia on student visa and is studying to be a chef, allegedly tried to force his way into the cockpit of Flight 128 shortly after 11.11pm from Melbourne to Kuala Lumpur last night.

He faces two charges against the Crimes Aviation Act, in an incident Victoria’s Police Commission Graham Ashton said is not terror-related.

Mr Marks’ lawyer told the court his client had a history of psychiatric illness and “has concerns for his safety in custody” due to his age.

Manodh Marks, 25, has been charged over allegedly threatening to blow up a Malaysia Airlines flight. (AAP)

The accused, dressed in a police-issued white forensic jumpsuit, did not appear in court and was remanded in custody. His lawyer made no application for bail.

Videos on Mr Marks’ Instagram page, posted only hours before the incident, purportedly show him driving along a highway listening to rap music with a cigarette.

One of the videos taken on Melbourne’s Bolte Bridge is captioned “on the way…”.

Mr Ashton said Mr Marks checked out of a psychiatric facility at Monash Medical Clinic, Clayton, yesterday and purchased his ticket on the flight shortly after.

The airplane was forced to return to Melbourne mid-air when Mr Marks allegedly tried to force his way into the cockpit, claiming to have a bomb.

The item was later found to be a “music speaker, about the size of a shoe”, Mr Ashton said.

Mr Ashton also defended the 90-minute wait passengers endured on the tarmac before police came on board to arrest the man.

"In some of those circumstances, if we had an incident where there were further explosives that were triggered, we could have had a mass casualty incident," he said.

"There were 337 passengers on that plane, plus crew, and we could have had a very serious incident.

"That was avoided through having a proper approach to getting the passengers off."

Passenger Stan Young said many on board didn’t know the item was not a bomb, and were forced to sit on the plane until police decided to enter.

“There was no communication. They left us waiting and wondering,” he said.

Victorian Premier Daniel Andrews backed the police approach.

"There's a standard process to work through and none of us can really know how traumatic it would have been," he said.

"It would have been certainly worse if police had rushed in and potentially made a bad situation much, much worse."

Malaysian Airlines said in a statement this afternoon that technical and cabin crew on the flight will not operate until further notice.

Among the passengers who subdued the man was Arif Chaudery, who sprung to action after a female crewmember raised the alarm.

"Families, kids, they were very scared, and some screaming…so three or four guys, we jumped as quickly as possible," Mr Chaudery told the TODAY Show.

"We just put him on the floor and finally staff brought the belt, so we handcuffed him and tied his legs and put his face on the floor.

"This could be worse, I can tell you that now, but that's 300 people who are safe."

Former Melbourne footballer Andrew Leoncelli also tried to stop the offender.

“We’d been going for about five to ten minutes. The hostesses were in an argument with somebody and the tone of that conversation changed very quicky,” he told 9NEWS.

An image purportedly taken on board MH128 shows a heavily armed officer in the aisle. (Supplied)

“I jumped out of the seat to confront the guy… He was threatening to blow the plane up which was pretty full on.

“You had to take the threat as genuine and real, we had no choice.”