HispanicBusiness

Fuel leaks from a Boeing 787 Dreamliner jet operated by Japan Airlines in January were caused by problems with a fuel tank valve, Japanese investigators said Friday.

A fuel leak on the jet during maintenance at Narita International Airport on January 13 was due to flaws in the valve's coating, the Transport Ministry said.

That led to a false signal that the valve was closed when it was actually open, the investigators said.

On January 8, the same jet had to return to the terminal at Boston's Logan International Airport after a fuel leak was detected while taxiing. The ministry said that a different valve failed to close because a foreign substance was believed to have been trapped.

On Friday, the ministry ordered Japan Airlines and All Nippon Airways, which also operates Dreamliners, to double check fuel systems and valves before flights.

Boeing's most sophisticated aircraft is also under investigation for possible battery problems after a Dreamliner jet made an emergency landing at an airport in western Japan in mid-January.

The incidents and others prompted the worldwide grounding of all Boeing 787s.