United Technologies, which builds the aircraft's auxiliary power unit, said it would also cooperate.

BBC: Dreamliner: Japan and US probe battery maker

Officials found that the battery for the aircraft's auxiliary power unit was incorrectly connected to the main battery that overheated.

BBC: Boeing 'set to offer plan to fix Dreamliner battery'

Flight 186's auxiliary power unit failed during the wait and the aircraft had to return to a gate.

WSJ: Flight Nightmares Overshadow Airlines�� Improving Record