'I think I'm about to die': Passengers reveal their terror after man threatened to 'blow up' Melbourne plane

Passengers have told loved ones they feared for their lives after a man onboard a late night Malaysia Airlines flight threatened to "blow up the plane" on Wednesday.

A 25-year-old man is now in custody following the incident that saw flight MH128 to Kuala Lumpur make an emergency landing at Melbourne's Tullamarine Airport less than 30 minutes into the flight.

The man had a large device and tried to storm into the cockpit before he was detained by passengers and cabin crew.

As the plane landed at Tullamarine just before midnight passengers sent messages to family and friends believing they were going to die.

The plane was forced to land back at Melbourne. Photo: 7 News

"it's just hitting me - it would have been the worst phone call," Carol Obradov, a relative of a passenger, told Sunrise.

Pictured: Distraught families wait at the airport for information. Photo: 7 News

"She sent messages to her mum and sister saying she thought she was going to die," Lachie Langord, a boyfriend of a passenger, said.

"It was pretty full on - for the better part of four hours my heart has been pounding."

Lachie Langford said it was a scary time. Photo: 7 News

One passenger Andy, told the story of how his fellow travellers detained the man who claimed to be carrying explosives.

"I could hear this idiot saying he wanted to see the pilot," he told Melbourne radio 3AW

"Cabin crew asked him to sit down and he responded 'Nah I'm not gonna sit down, I'm gonna blow this f''''''ing plane up'.

"I thought to myself that this guy's serious, we better do something, so I approached him," he added.

"He went down the side and two lads at the back grabbed him and held him down."

Passenger detained after threatening to blow up plane
The flight landed at Melbourne's Tullamarine Airport before heavily armed forces boarded the plane.

More than seven hours after the incident, most of the flight's 220 passengers remain at the scene as they provide their statements to police.

Malaysai Airlines said the passengers are being accommodated at hotels and will be offered travel on the next available flight or on other carriers.

Officials boarded the plane and told everyone to remain in their seats. Photo: 7 News

Police have praised passengers for their effort.

"I imagine it would have been quite frightening for them [the passengers] and it was quite heroic for passengers and crew to restrain this person," Superintendent Tony Langdon from Victoria Police said.

Police confirmed the device the man had - a black item, shaped like a watermelon with antennas coming out of it - was not an explosive.

They said the man has a history of mental illness.

According to a report in Malaysia's The Star, Deputy Transport Minister Datuk Seri Ab Aziz Kaprawi said the disruptive passenger, thought to be a Sri Lankan national, was drunk.

The airline stressed that "at no point was the aircraft 'hijacked'".

Officials managed to put the man in custody. Photo: 7 News