A co-pilot who sent his Japanese passenger jet into a nosedive when he mistook a rudder control for a door lock did not notice anything was wrong for 17 seconds, a government report last week.
The All Nippon Airways (ANA) flight, with 117 passengers and crew on board, dived 1900 metres in 30 seconds from a height of about 41 000 feet.
The flight, bound for Tokyo from Okinawa, almost turned upside down during the incident on 6 September last year, the Japan Transport Safety Board said.
The plunge happened over the Pacific Ocean when the co-pilot, who worked for a now defunct subsidiary of ANA, tried to unlock the cockpit door for the captain after he had been to the toilet.
Instead of the door lock, the co-pilot touched the rudder control, sending the plane veering to the right, before it lurched back to the left.
A chronology included in the written report showed that the co-pilot only noticed something was wrong 17 seconds after the rudder was operated.
Images from the flight recorder on the Boeing 737-700 showed the plane dropped sharply and tipped more than 130 degrees to the left at one point.
However, because it was dark outside, many of those onboard did not realise the plane had almost flipped over, the report said.
Two crew members suffered minor injuries but the plane later touched down safely at Tokyo's Haneda Airport.