Almost three weeks into its investigation, and with the global fleet of Boeing 787s grounded, the NTSB said on Sunday it hasn't found the root cause of the lithium-ion battery fires aboard two of the Dreamliners. Investigators in Arizona found nothing wrong with the airplane's auxiliary power units, the NTSB said. On Monday, Japan's Transport Ministry said investigators found no problems at GS Yuasa, in Kyoto, where the batteries are manufactured. Inspectors now are checking the systems that monitor the battery. Meanwhile, a financial analysis by Jefferies & Co. found the grounding will likely cost Boeing more than $500 million, and in a worst-case scenario, up to $5 billion, according to Bloomberg.
Airline analyst Robert Mann told the Guardian that if the battery itself and the charging process are not found to be the cause of the problems, "you are left with intermittent faults, which are very difficult to track down, or some unintended consequence from a usage problem." He added that since both problems occurred on Japanese airplanes, which tend to fly shorter legs than the other 787 operators, perhaps those batteries were charged more frequently. "But I am grasping at straws," Mann said. "As is everyone. A lot smarter people than me are looking at this." On Wednesday, Boeing CEO Jim McNerney is expected to speak publicly about the airplane's problems for the first time, when he unveils the company's latest financial report.