The Directorate General of Civil Aviation (DGCA) reached this conclusion while probing the incident involving a brand new Boeing 737-800 aircraft coming to Pune from Dubai, just four days after the crash in Mangalore of a similar airplane that claimed 158 lives.
However, no one was injured in the May 26 incident as the commander soon returned to his seat, took control of the aircraft and landed safely at Pune. The co-pilot was not trained to recover aircraft flying on an auto-pilot mode, the DGCA said in its final inquiry report.
The DGCA recommended "appropriate action" against the crew involved and asked Air India Express to review its training curriculum, including simulator training of pilots to meet with such in-flight emergencies.
The incident occurred when the commander of the aircraft, which was then flying on the auto-pilot mode, got out of the cockpit to go to the washroom.
After finding the washroom occupied, he tried to re-enter the cockpit but found the door locked from inside. On getting no response from the co-pilot, he entered it using emergency keys.
By that time, the aircraft was on a descending mode and had gone down by about 2,000 feet and still moving rapidly below the flight path. The chief pilot slowly gained control but the plane had already dived 5,000 feet.
The co-pilot told the probe panel that he was doing some technical paper work. While "adjusting his seat forward", he "inadvertently pressed the Control Column forward" which led the auto-pilot to start the descending roll.
The DGCA probe found that the co-pilot "panicked" and gave wrong commands which caused the aircraft to bank.
The commander, after he entered the cockpit, also took certain steps "without coordination with co-pilot" which also contributed to the incident. But the plane was put right back on track and made a safe landing on reaching Pune.
The entire incident occured within a span of three-four minutes.
"The incident occured due to inadvertent handling of the control column in fully automated mode by the co-pilot, which got compounded as he was not trained to recover the aircraft in automated mode," the report said.