The Boeing 787 Dreamliner bound for London from the Indian city of Ahmedabad began to lose thrust and sink shortly after taking off in June, according to the report released on Saturday by Indian accident investigators.
The crash was the world's deadliest aviation accident in a decade, killing all but one of the 242 people on board and 19 others on the ground.
The report by India's Aircraft Accident Investigation Bureau about the June 12 crash raises questions over the position of the critical engine fuel cutoff switches.
Almost immediately after the plane lifted off the ground, closed-circuit TV footage showed a backup energy source called a ram air turbine had deployed, indicating a loss of power from the engines.
In the flight's final moments, one pilot was heard on the cockpit voice recorder asking the other why he cut off the fuel.
"The other pilot responded that he did not do so," the report said.
It did not identify which remarks were made by the flight's captain and which by the first officer, nor which pilot transmitted "Mayday, Mayday, Mayday" just before the crash.
The commanding pilot of the Air India plane was Sumeet Sabharwal, 56, who had a total flying experience of 15,638 hours and, according to the Indian government, was also an Air India instructor.
His co-pilot was Clive Kunder, 32, who had 3403 hours of total experience.
The fuel switches had almost simultaneously flipped from run to cutoff just after takeoff. The preliminary report did not say how the switches could have flipped to the cutoff position during the flight.
The crash is a challenge for Tata Group's ambitious campaign to restore Air India's reputation and revamp its fleet, after taking the carrier over from the government in 2022.
Air India acknowledged the report in a statement. The carrier said it was co-operating with Indian authorities but declined further comment.
Experts have said a pilot would not be able to accidentally move the fuel switches.
"If they were moved because of a pilot, why?" asked US aviation safety expert Anthony Brickhouse.
The switches flipped a second apart, the report said, roughly the time it would take to shift one and then the other, according to US aviation expert John Nance.
He said a pilot would normally never turn the switches off in flight, especially as the plane was starting to climb.
Flipping to cutoff, which almost immediately cuts the engines, is most often used to turn engines off once a plane has arrived at its airport gate and in emergencies such as an engine fire.
The report does not indicate there was any emergency requiring an engine cutoff.
At the crash site, both fuel switches were found in the run position and there had been indications of both engines relighting before the low-altitude crash, the report said.
The US National Transportation Safety Board thanked Indian officials for their co-operation and noted there were no recommended actions in the report aimed at operators of Boeing 787 jets or the GE engines.
The US Federal Aviation Administration said it was committed to addressing any risks identified throughout the process.
Boeing said it continued to support the investigation and its customer, Air India.
GE Aerospace did not respond immediately to a request for comment.
Most air crashes are caused by multiple factors, with a preliminary report due 30 days after the accident, according to international rules, and a final report expected within a year.
The plane's black boxes, combined cockpit voice recorders and flight data recorders, were recovered in the days following the crash and later downloaded in India.
