You'd think the button for the cockpit door and the actual controls for a plane would be easily distinguishable, especially to a pilot.
But not for one un-named co-pilot on an All Nippon Airways flight whose mistake nearly caused a major catastrophe.
The co-pilot had been asked to take over the controls of a passenger plane whilst the captain went to the toilet. In trying to unlock the cockpit door for the captain's return, he mistook a command button for the cockpit door lock switch. This caused the plane to plunge, almost turning upside down.
The ANA flight, with 117 passengers and crew on board, dived 1900 metres in 30 seconds in the incident on September 6, according to Japan's transport ministry.
The plane later managed to touch down safely at Tokyo's Haneda airport. Two crew members were slightly injured.
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. A senior ANA official apologised to travellers for any distress caused by the incident.