The pilot and copilot of an All Nippon Airways plane were unaware for 17 seconds that their aircraft almost turned upside down during a flight last year, the Japan Transport Safety Board (JTSB) said Friday in a report on the incident.
The ANA flight, with 117 passengers and crew on board, dived 1,900 meters in 30 seconds in the incident off the southern Shizuoka district on Sept 6, 2011.
The maneuver happened when the co-pilot, in trying to unlock the cockpit door for the captain who was returning from the toilet, mistook a command button for the cockpit door lock switch nearby.
A chronology included in the JTSB's report showed that the co-pilot only noticed something was wrong 17 seconds after the rudder was operated.
The plane, which took off from Naha in Okinawa in the south, later managed to touch down at Tokyo's Haneda airport safely.
Two crew members were slightly injured, while four passengers reported health problems following the incident.
Images from the flight recorder on the Boeing 737-700 showed the plane veered to the right and then sharply to the left, before dropping backwards.
The aircraft tipped more than 130 degrees to the left at one point, but the darkness outside meant many of those on board did not realize the craft had almost flipped over.© Japan Today/AFP