Japan govt: 787 test flights not part of certification process

But says it could help the firm prepare for later battery test flights

Japan's transport ministry said on Tuesday Boeing Co's test flight of its troubled Dreamliner jets would not be part of its certification process but could help the firm prepare for later battery test flights.

Boeing's Dreamliner jets have been grounded worldwide since January after two separate incidents with a lithium-ion battery on board Japan Airlines Co Ltd and All Nippon Airways Co Ltd flights.

The US aircraft maker said the two-hour 787 test flight on Monday "went according to plan" and it would go ahead with another flight test to gather data to be submitted to the US Federal Aviation Administration.

Japan's Civil Aviation Bureau, however, said on Tuesday it was still too early to comment on when Boeing's 787 flights might resume.