Analysis of a flight recorder from that plane showed that a lithium-ion battery experienced a sudden drop in voltage and was not overcharged, the Japan Transport Safety Board said Wednesday.

CNN: What's wrong with the Dreamliner?

To identify the necessary repairs, Boeing says it worked closely with equipment suppliers and investigators at the National Transportation Safety Board and the Japan Transport Safety Board, spending spent more than 100, 000 hours developing test plans, building test rigs, conducting tests and analyzing the results to ensure the proposed solutions met all requirements.

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