TOKYO (REUTERS) - Japan's transport minister acknowledged that passenger confidence in Boeing Co's new 787 Dreamliner jet is at stake, as both Japan and the United States have opened broad and open-ended investigations into the plane after a series of incidents that have raised safety concerns.

Japanese authorities said on Monday they would investigate fuel leaks on a 787 operated by Japan Airlines Co, and the U.S. National Transportation Safety Board said later its agents would analyse the lithium-ion battery and burned wire bundles from a fire aboard another JAL 787 at Boston's Logan Airport last week.

The Dreamliner, the world's first mainly carbon-composite airliner, is billed as Boeing's most fuel-efficient jet and a potential game-changer for civil aircraft. It was initially scheduled to enter service in May 2008, but production delays held up its commercial debut until late last year.

The sophisticated new plane suffered a series of mishaps last week - two fuel leaks, the battery fire, a wiring problem, brake computer glitch and cracked cockpit window - increasing scrutiny on a plane that has a list price of US$207 million (S$253 million).

"Looking at this from the point of view of average citizens, having these sort of incidents occur seemingly day after day, one could become very uneasy," Mr Akihiro Ota told reporters at a ministry briefing on Tuesday. He said there was no deadline for reporting the outcome of the investigation.

"We plan to look into the scale of these accidents and what the overall situation is. We will convey the message to those who operate (the plane) that it is absolutely necessary to be safe," Mr Ota said.

While many of the 787's mishaps are considered routine for a new design entering service, the daily toll has heightened concerns about the aircraft's safety. More than 800 of the planes have been ordered by airlines around the world.

Japan is the biggest market so far for the Dreamliner, with JAL and local rival All Nippon Airways Co flying 24 of the 50 Dreamliners delivered to date.

Separately, Fuji Heavy Industries Ltd said it had not been informed of any production changes for the Dreamliner in the wake of the model's recent issues. The company is the sole supplier of the Dreamliner's wing box - where the plane's wings connect to the fuselage - from its plant in Nagoya, central Japan.

"At the moment, absolutely no," Fuji Heavy's deputy-president Jun Kondo said in response to a reporter's question about potential modifications to the aircraft.