The first comprehensive report into the mystery of Malaysia Airlines Flight 370 has revealed that the battery of an underwater locator beacon had expired more than a year before the plane vanished in March 2014.

Apart from that anomaly, the detailed report released Sunday devoted pages after pages to describe the complete normality of the flight, shedding little light on aviation's biggest mystery.

The significance of the expired battery was not immediately apparent, except indicating that searchers would have had lesser chance of locating the aircraft in the Indian Ocean, where it is believed to have crashed, even if they were in its vicinity.