The 787 relies more than any other modern airliner on electrical signals to help power nearly everything the plane does. It's also the first Boeing plane to use rechargeable lithium ion batteries, which charge faster and can be molded to space-saving shapes compared to other airplane batteries. The plane is made with lightweight composite materials instead of aluminum.
The U.S. National Transportation Safety Board said it is sending an investigator to Japan to join the probe.
The U.S. Federal Aviation Administration said the incident will be included in a comprehensive review it began last week of the 787's critical systems, including design, manufacture and assembly. U.S. government officials have been quick to say that the plane is safe. Nearly 50 of them are in the skies now.
GS Yuasa Corp., the Japanese company that supplies all the lithium ion batteries for the 787, had no comment as the investigation was still ongoing. Thales, which makes the battery charging system, had no immediate comment.
In Tokyo, the transport minister, Akihiro Ota, said authorities were taking the incidents seriously.
"These problems must be fully investigated," he said.
Boeing has said that various technical problems are to be expected in the early days of any aircraft model.
"Boeing is aware of the diversion of a 787 operated by ANA to Takamatsu in western Japan. We will be working with our customer and the appropriate regulatory agencies," Boeing spokesman Marc Birtel said.
In Wednesday's incident, a cockpit instrument showed a problem with the 787's battery and the pilot noticed an unusual smell, the airline said. The flight requested and was granted permission to make an emergency landing at Takamatsu airport.
Aviation safety expert John Goglia, a former National Transportation Safety Board member, said the ANA pilot made the right decision.
"They were being very prudent in making the emergency landing even though there's been no information released so far that indicates any of these issues are related," he said.
But much remains uncertain about the problems being experienced by the 787, said Masaharu Hirokane, analyst at Nomura Securities Co. in Tokyo.
"You need to ensure safety 100 percent, and then you also have to get people to feel that the jet is 100 percent safe," Hirokane said.
AP Business Writer Kelvin Chan in Hong Kong and AP Transportation Writer Joan Lowy in Washington, D.C., contributed to this report.
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