Boeing will begin flight tests of its 787 Dreamliner on Saturday morning to gather data on the battery system that has caused the in-service 787 fleet to be grounded, according to an inside source.

The plane that will fly Saturday is Dreamliner No. 5, one of six planes filled with measuring equipment that was used in the flight tests for the 787’s original Federal Aviation Administration (FAA) certification.

Ground tests were successfully completed on the jet Friday.

On Thursday, the FAA granted Boeing’s request to do test flights specifically to gather data on the battery performance in flight.

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The FAA has imposed strict operating conditions on the test flights, requiring preflight inspections and in-flight monitoring of the battery system.

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