US safety officials investigating a battery fire on a Boeing 787 opened a two-day public hearing Tuesday to examine how the pioneering lithium-ion battery system was designed and approved for use.
Three months after the 787 was grounded worldwide because of overheated batteries, the National Transportation Safety Board was reviewing presentations by Boeing, contractors and the Federal Aviation Administration.
"The NTSB is holding this hearing to explore the battery's original design and certification," said Debbie Hersman, chair of the safety board.
"We are here to understand why the 787 experienced unexpected battery failures following a design program led by one of the world's leading manufacturers and a certification process that is well-respected throughout the international aviation community."
Investigators still have yet to pinpoint the cause of a January 7 battery fire on a Japan Air lines 787 parked at a Boston airport, the incident under NTSB investigation.
After battery fumes forced an emergency landing of an All Nippon Airways 787 in Japan on January 16, the FAA and other regulators ordered all 50 Boeing 787s in service grounded.
Last Friday the FAA approved Boeing's battery fix, a major step forward in returning the cutting-edge plane to the skies.
On Tuesday, the European Aviation Safety Agency announced its approval of the Boeing battery system modifications.
Japanese regulators said Tuesday that they would make a final decision on allowing the 787 to fly as early as this week.
"We will make the final decision on whether to resume the operation after studying the results" of the NTSB hearing, Transport Minister Akihiro Ota told reporters in Tokyo.
All Nippon Airways, the biggest 787 operator, and Japan Airlines, have begun replacing the novel battery systems on the troubled aircraft after the FAA approved the modifications.
ANA said the modifications could take as long as two months, with the carrier eying a resumption of flights in June. JAL has not given any timeline for restarting flights.
United Airlines is the sole US carrier flying the 787.
At the NTSB hearing Tuesday, officials heard presentations on the design of the lithium-ion batteries and the FAA certification process that relied heavily on testing and conclusions from Boeing.
The FAA approved the battery use under "special conditions," saying that the airworthiness regulations did not contain adequate or appropriate safety standards.
Critics have argued that the FAA overly relies on company testing and should step up its own oversight.
NTSB chief Hersman said that the safety board was looking for "lessons learned not just for the design and certification of the failed battery, but also for knowledge that can be applied to emerging technologies going forward."
"Today, more than ever before, with the rapid evolution of new technologies and the growing complexity of components and systems, it's imperative to understand how best to oversee their development and certification."
Boeing shares were up 1.4 percent in afternoon trade in New York. The company is set to report first-quarter earnings before the market opens Wednesday.