The battery on one of Malaysian Airline flight MH370's data recorder beacons may have expired more than a year before the plane went missing, according to the nearly 600-page interim safety-investigation report released by Malaysia's transport ministry Sunday.
"According to maintenance records, the SSFDR ULB (solid state flight data recorder underwater locater beacon) battery expired in December 2012. There is no evidence to suggest that the SSFDR ULB battery had been replaced before the expiry date," the report said.
"While there is a definite possibility that a ULB, will operate past the expiry date on the device, it is not guaranteed that it will work or that it would meet the 30-day minimum requirement," it said. "There is also limited assurance that the nature of the signal (characteristics such as frequency and power) will remain within specification," the report said.
Read More Malaysia Airlines: One year after MH370
The commercial plane operated by Malaysia's flagship carrier vanished during a routine flight from Kuala Lumpur to Beijing on March 8, 2014; debris has yet to be found. What caused the plane to disappear remains a topic of speculation and has become one of the aviation world's biggest mysteries to date.
Investigation of various radar and tracking data indicate it flew far off course before disappearing into the Indian Ocean.
The captain ordered enough fuel for seven hours and 31 minutes of flight, compared with a planned flight duration of 5 hours and 34 minutes, the report said.
Searchers had initially focused on trying to detect "pings" from the beacons on the flight recorders, known as black boxes.