The report was presented in Kuala Lumpur by the investigator-in-charge of the Malaysian Safety Investigation Team for MH370, Kok Soo Chon.
"We can conclude that MH370 had turned back and the turn back was not because of anomalies in the mechanical system. The turn back was made not under autopilot but under manual control. Everyone participating in the investigation agreed that the autopilot was off at the time of the turn," he said during the presentation.
The investigation team found several violations of the safety protocols, including a 20-minute delay in the first attempt to establish communication with the plane by the flight operation officers of Ho Chi Minh City airport, that delayed the discovery of the fact that the aircraft changed course, Kok Soo Chon said.
Nevertheless, disruptions and further loss of communication might have been caused by the manual disconnection of communication systems in the pilot's cockpit, he added.
The commission has not yet determined the reasons of the aircraft's disappearance, and the location of the main part of the wreckage remains unknown, the head of the commission said.
Flight MH370, en route from Kuala Lumpur to Beijing, disappeared from radars on March 8, 2014, less than an hour after takeoff. There were 227 passengers and 12 crew members on board the aircraft.
So far, several pieces of debris believed to have come from the aircraft have been found at different locations, including Mozambique, South Africa and the French island of Reunion in the Indian Ocean.