The inquiry report, prepared by a team of 19 investigators from Malaysia and seven other nations including the U.S., Australia and China, said that the battery on the beacon had expired in December 2012 and no record was available to show that it was replaced. Flight 370 vanished from radar in the small hours of March 8 last year, less than an hour into its flight to Beijing from Kuala Lumpur.

“As stated in the findings of the report, the engineering maintenance system was not updated correctly when the ULB [underwater locating beacon] battery was first installed. This was a maintenance scheduling oversight,” Malaysia Airlines said. The engineering maintenance system is used to track maintenance and alert engineers about parts that need to be replaced.

The cockpit voice recorder and flight data recorder on commercial aircraft, together called the black boxes, are equipped with beacons to help locate them underwater. The battery in the beacon is designed to power its signals for at least 30 days.

The search for Flight 370 deep in the Southern Indian Ocean picked up faint signals that could have potentially come from the plane’s beacons, but they were soon lost. The signals were picked by sonar equipment close to the expiration of the 30-day life of the batteries and it was never confirmed if they actually came from the wreckage of Flight 370.

The inquiry report said the effectiveness of the beacon may decrease once the battery expires.

Malaysia Airlines said the battery on a similar beacon attached to the cockpit voice recorder was within its valid life and that that beacon would have transmitted signals for 30 days after it was immersed in water.

No trace has been found of the Boeing 777-200 jet or the 239 passengers and crew on board, but experts have used a new satellite signal-based analysis technique to determine that the plane kept flying for several hours after it deviated off course, before ending in a remote part of the ocean west of Australia. A search team led by Australia is currently looking for the plane in a 60,000 square kilometer area, where the plane is estimated to have gone down.

Malaysia Airlines said it has taken significant steps to improve safety after the loss of Flight 370. Malaysia Airlines said since December, its Boeing 777s report their position every 15 minutes, from 30 minutes when Flight 370 disappeared. Other planes on the company’s fleet, which includes Boeing 737-800, Airbus A380 and Airbus A330 jets, now report data on their location every 10 minutes.

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