The turn-back "was not because of anomalies in the mechanical systems. we can confirm the turn-back. was made under manual control".
Kok said the team looked into the pilot and first officer's background.
MH370's cargo included 221 kilograms (487 pounds) of lithium batteries and 4.6 tons of fresh mangosteen fruit, according to its manifest. The search was backed by the Malaysian government, which was offering a bounty for the plane if it was found.
It did, however, highlight mistakes and protocols and guidelines that were not followed, the families told reporters after a briefing on the report.
The report, prepared by a 19-member global team, reiterated Malaysia's assertion the plane was deliberately diverted and flown for over seven hours after severing communications. "The (investigative) team has been given full freedom in conducting the investigation and not a single edit or amendment has been made to the report", he said.
Malaysia's Transport Minister Anthony Loke had promised that relatives of those who were on board would be briefed about the report before it was publicly released.
Malaysia had signed a "no find, no fee" deal with Ocean Infinity to resume the hunt after the official search led by Australia, Malaysia and China was called off in early 2017.
Today's report comes two months after Malaysia called off a privately funded underwater search for the aircraft.
Air traffic controllers did not initiate emergency procedures in a timely fashion, delaying the start of the search and rescue operation, it said. However, investigators say they are confident the aircraft was deliberately flown off course and into the Indian Ocean.
It was the second major search after Australia, China and Malaysia ended a fruitless $200 million-search across an area of 120,000 square kilometres a year ago. "Safety is not something to be taken lightly", she said. It is believed to have crashed in the southern Indian Ocean, hundreds of miles away from its scheduled route.
Pieces of aircraft debris found washed up on the coast of east Africa and the French island of Réunion, thousands of kilometers from the likely crash site, were confirmed to be from the Boeing Co.
Theories range from mechanical error or a remote-controlled crash, to more freaky explanations like alien abduction and a Russian plot.