MH370 report: Black box battery expired a year before plane vanished

The 584-page report, titled Factual Information Safety Investigation for MH370, said maintenance records showed that the battery on the beacon attached to the Flight Data Recorder, commonly known as the 'black box', expired in December 2012.

"There is some extra margin in the design to account for battery life variabilty and ensure that the unit will meet the minimum requirement," the report said.