Aviation inspectors have found a key part missing in a Boeing jetliner during an emergency probe after a similar plane exploded last week in southern Japan, officials said Friday.
Inspectors found a washer missing from a wing slat in a Boeing 737-700 airplane owned by Air Nippon, an oversight that could lead to a bolt coming loose, said Transport Ministry official Atsushi Shimamura.
On Aug. 20, a China Airlines Boeing 737-800 landed at Okinawa's Naha airport and exploded in a fireball, seconds after all 157 passengers and eight crew had evacuated safely onto the tarmac.
Investigators found a bolt on the right wing slat had come loose and pierced a fuel tank, causing fuel to gush out and catch fire. Later, three parts including a washer were found near the fuel tank.
Authorities, however, do not yet know whether the bolt came loose because the washer was not in place.
Shimamura said that inspectors had not reached a conclusion about why the washer was missing from the Air Nippon plane, but that it was possible the mistake was made during production of the plane. Air Nippon had used the new aircraft since January.
Transport Minister Tetsuzo Fuyushiba also told reporters that the part may have been missing been due to a production error.
"This airplane was almost brand-new. Judging from the facts that (the washer) was missing and it was not found anywhere nearby, we suspect something that should have been in place was not in place in the process of manufacturing," he said.
Boeing spokesman Mark Hooper in Hong Kong said he could not comment on this particular case, but he pointed to a Boeing statement saying the Chicago-based company was examining the plane's design and production to find a cause for the fire.
Following the China Airlines explosion, officials had been ordered to inspect all Boeing's newer 737 jetliners in Japan. There are 23 of them owned by three airline companies.
The ministry reported the findings Thursday to the U.S. Federal Aviation Administration, and asked it to investigate and consider preventive measures, Shimamura said.
Meanwhile, Air Nippon also notified Boeing of the problem and asked for investigations, he said.
Slats, stored inside the main wings during flight, slide out from the frontal edge of the main wings during takeoff and landing to help lift the aircraft, along with flaps that come out of the wings' rear edge.
No irregularity was found in the 22 other similar jetliners, Shimamura said. Skymark and Japan Airlines each own five Boeing 737-800s while Air Nippon, part of the All Nippon Airlines group, has 13 Boeing 737-700s.
Separately, regional carrier Skynet Asia grounded one of its 737-400 jets after a metal fragment was found in the left engine during routine maintenance overnight, public broadcaster NHK and Kyodo News agency said.
Workers found the engine's exhaust temperature was running higher than normal, and discovered the fragment, they said. The airline planned to replace the engine and determine the source of the one-square-centimeter (one square half-inch) fragment.