“The team is unable to determine the real cause for the disappearance of MH370,” concluded the largely technical report, noting that Malaysian government investigators were hindered in their probe as neither the plane’s wreckage nor its black boxes had been found.

Kok Soo Choon, head of the MH370 safety investigation team, told reporters in Kuala Lumpur: “Answers can only be conclusive if the wreckage is found.”

The report’s authors will head to Beijing to brief relatives there, as almost two-thirds of the plane’s passengers were Chinese nationals.

In the days after the plane vanished, various theories surfaced, from a systems failure to mechanical problems to pilot error or a hijacking incident.

In the report, the 19-member team pointed to failings by air traffic controllers, said the course of the Malaysia Airlines plane was changed manually, and refused to rule out that someone other than the pilots had diverted the jet.

Investigators played down concerns about the pilot and first officer, saying neither appeared to have suffered difficulties in their personal lives that could have affected their ability to fly.

“We did not find any change to their behaviour, everything was normal,” Kok said.

The report also said the plane was airworthy and did not have major technical issues, with Kok saying it had been diverted from its intended flight path manually.

On the theory that the plane had been taken over remotely to foil a hijacking, the report said intervention by a third party could not be ruled out. But there was no evidence to suggest the plane was flown by anyone other than the pilots, it added.

For the plane to veer off course, “it is more likely that such manoeuvres are due to the systems being manipulated.”

One area that came in for criticism in the report by the team, which included foreign investigators, was air traffic control.

It said both Malaysian air traffic control and their Vietnamese counterparts failed to act properly when the Boeing jet passed from Malaysian to Vietnamese airspace and disappeared from radars.

Air traffic controllers did not initiate emergency procedures in a timely fashion, delaying the start of the search and rescue operation, it said.

Relatives who were briefed at the transport ministry in the administrative capital Putrajaya before the report’s public release expressed anger that there was nothing new in the document, with some storming out of the briefing as frustration boiled over.

“It is so disappointing,” said Intan Maizura Othman, whose husband was a steward on MH370, which had been flying from Kuala Lumpur to Beijing carrying mostly mainland Chinese passengers when it vanished.

“I am frustrated. There is nothing new in the report.”

She said the meeting between relatives and officials descended into a “shouting match” as anger mounted.

G. Subramaniam, who lost a son on the flight, added that “unsatisfactory responses left many angry”.

Chinese Foreign Ministry spokesman Geng Shuang said Beijing had paid close attention to the MH370 investigation.

“We hope that all sides can continue to remain in close contact and coordination, to properly carry out relevant follow-up work,” he told a daily news briefing, without elaborating.

Malaysia Airlines flight 370: the conspiracy theories

The disappearance of MH370 triggered the largest hunt in aviation history. But no sign of it was found in a 120,000-square kilometre (46,000-square mile) Indian Ocean search zone and the Australian-led hunt was suspended in January last year.

US exploration firm Ocean Infinity resumed the search in a different location at the start of this year on a “no find, no fee” basis, using hi-tech drones to scour the seabed. But that search was also called off after failing to find anything.

Only three confirmed fragments of MH370 have been found, all of them on western Indian Ocean shores, including a two-metre wing part known as a flaperon.

Malaysia’s new government, which took power in May, has said the hunt could be resumed but only if new evidence comes to light.

Transport Minister Anthony Loke insisted Monday that “the aspiration to locate MH370 has not been abandoned and we remain ever-hopeful that we will be able to find the answers we seek when the credible evidence becomes available”.