THE mysterious route taken by doomed flight MH370 before the plane vanished with 239 souls on-board has been re-examined by aviation experts who claim to have made chilling new discoveries.

For more than four years the world has grappled with questions over how the Boeing 777 airliner vanished into thin air en route to Beijing from Kuala Lumpur.

And now several experts who have worked to determine what brought the plane down say they have more answers.

According to Senior Boeing 777 pilot and instructor Simon Hardy, MH370 was used in a murder-suicide mission by Captain Zaharie Amad Shah, who deliberately flew the aircraft over his hometown of Penang for an “emotional goodbye”, before ditching it in the Southern Indian Ocean “where it could never be found”.

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In a 60 Minutes episode that aired on Sunday night, Mr Hardy said he made a discovery by reconstructing Mr Zaharie’s flight plan from the military radar. He said Mr Zaharie had avoided detection of the plane by either Malaysian or Thai military radar by flying along the border, crossing in and out of each country’s airspace.

It was also on the border that the plane’s transponder suddenly turned off.

“As the aircraft went across Thailand and Malaysia, it runs down the border, which is wiggling underneath, meaning it’s going in and out of those two countries, which is where their jurisdictions are,” Mr Hardy told the program.

“So both of the controllers aren’t bothered about this mysterious aircraft. Cause it’s, ‘Oh, it’s gone. It’s not in our space anymore’.”

Mr Hardy said the manoeuvres were clearly deliberate.

“If you were commissioning me to do this operation and try and make a 777 disappear, I would do exactly the same thing,” he said.

“As far as I’m concerned, it’s very accurate flying and I think it did the job, because we know, as a fact, that the military did not come and intercept the aircraft.”

There has been much speculation as to why the plane went so far off course and “dipped the wing” over Penang before making a sharp turn and heading south for the next six hours. According to Mr Hardy, it was so the pilot could see his hometown one last time.

“I spent a long time thinking about what this could be, what technical reason is there for this?” he said.

“And after two months, three months of thinking about it, I finally got the answer — somebody was looking out the window.

“It might [have been] a long, emotional goodbye or a short, emotional goodbye to his hometown.”

Mr Hardy was one of several aviation experts who appeared on the program to re-examine MH370 evidence and look at whether or not the tragedy was a deliberate act of murder carried out by Mr Zaharie.

Former Senior Investigator with the Transportation Safety Board of Canada, Larry Vance, told 60 Minutes he was confident he knows what happened to the aircraft.

“I think the general public can take comfort in the fact that there is a growing consensus on the plane’s final moments,” he said.

Mr Vance said the pilot “was killing himself” and took the aircraft to the most remote place possible so it would “disappear”.

“Unfortunately, he was [also] killing everybody else on board, and he did it deliberately,” he said.

“He was taking it to a predestination, some place that he had planned to take it, and he flew that six hours to get it there.”

Mr Vance said he envisioned the plane on the bottom of the ocean, with the fuselage in one piece and the left wing still on.

“The right wing may be off, the engines are separate, but you basically have four pieces of aeroplane down there,” he said.

“It’s not scattered all over the bottom of the ocean.”

In 2016 Prime Minister Malcolm Turnbull unexpectedly said it was “very likely that the captain planned this shocking event”.

John Dawson, a lawyer who represented nine families from MH370 and MH17, recently told News Corp Australia the evidence pointed squarely to one of the aircrew being responsible.

“In MH370, you have the pilot flying between Malaysia and Beijing who turns back the aircraft. The evidence is so heavily weighted to involvement by one of the aircrew taking this aircraft down.

“That aircraft has probably depressurised, the people died of asphyxiation, it was premeditated murder. It was highly planned. The bodies have never been found.”

But despite experts’ observations, the Malaysian government, which has signed a “no cure, no fee” deal with Texas-based company Ocean Infinity to resume the hunt for the plane, remains silent on the question of Mr Zaharie’s possible involvement.

Ocean Infinity started the search on January 22 this year, following a failed $200 million search for the plane. At the time, experts said they expected to have answers within a matter of weeks.

The company has 90 search days to look for the plane, which has been spread over several months.

Officials said there was roughly an 85 per cent chance of finding traces of the wreckage in a new 25,000 square kilometre search area.

The investigation is expected to end in mid-June.

MH370 Mystery: strange new information MH370 Mystery: strange new information

megan.palin@news.com.au | @Megan_Palin