The China Eastern Airlines plane that crashed in March, killing 132 people, appears to have been flown into a mountainside by someone at the controls, according to reports.
The black box flight recorders show that the plane was forced into a dive by the cockpit.
The plane did what it was told to do by someone in the cockpit, according to an unnamed source quoted by the Wall Street Journal.
The China Eastern plane was cruising at a steady altitude and speed before it suddenly descended more than 20,000ft in just over a minute and crashed near the city of Wuzhou.
US officials are involved in the crash inquiry because the plane is US-made.
While the design of the later model of Boeing's plane was involved in two fatal disasters in the last year, it has been in use around the world for a long time.
Aviation experts noted that the flight pattern shown on tracking sites resembled the Germanwings crash in 2015. The pilot of the plane deliberately crashed it into the French Alps, killing 150 people.
The WSJ reported that Chinese authorities have not told the US that there was a mechanical problem with the plane.
The pilot and co-pilot had no known financial or family issues, according to China Eastern. No emergency code was sent from the plane, suggesting that no one could have gotten into the cockpit, according to authorities in China.
China's air regulator said last month that investigators were continuing their inquiries.