Torn insulation on a cockpit cable — and not a mobile phone — might have been the cause of the communications breakdown that delayed an All Nippon Airways flight Wednesday, the transport ministry said.
But the ministry also said Thursday it was impossible to determine the exact cause of the mishap, which delayed 225 passengers at Nagasaki airport and surprised mobile phone users across the country Wednesday.
ANA initially blamed interference from a passenger's cell phone for delaying a Boeing 767-300 that was about to take off.
After inspecting the plane, however, the carrier Thursday found a tear in the rubber skin of a cable connecting the captain's microphone to the cockpit's radio system.
The rip might have created a short circuit that caused the microphone system breakdown, it said. But the cell phone has not yet been ruled out as the cause of the communications failure, the ministry said.
After a flight attendant asked all passengers to switch off their mobile phones, the radio equipment started functioning normally again and the plane departed for Haneda airport 44 minutes behind schedule.
Similar communication trouble caused by cell phone use has been reported many times in the past, including another incident in Japan that took place in June 1998, the ministry said.
"Using a mobile phone inside an airplane is prohibited by the Civil Aeronautics Law. It's punishable by a fine of up to ¥500,000," a transport ministry official said.