The battery of an underwater locator beacon had expired more than a year before the Malaysia Airlines flight MH370 vanished last March, the first comprehensive report into the mystery has revealed
Apart from that anomaly, the detailed report devoted page after page to describe the complete normality of the flight, shedding little light on aviation's biggest mystery.
"The sole objective of the investigation is the prevention of future accidents or incidents, and not for the purpose to apportion blame or liability," the report said.
The significance of the expired battery on the beacon of the Flight Data Recorder 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.
However, the report said that the battery on the locator beacon of the cockpit voice recorder was working.
Even though the battery on the beacon had expired, the instrument itself was functioning properly and would have in theory captured all the flight information.
The two instruments are critical in any crash because they record cockpit conversation and flight data, leading up to the end of the flight.
The 584-page report by an independent investigation group went into minute details of the crew's lives - their medical and financial records, their training before detailing the aircraft's service record - as well as maintenance schedule, weather, communications systems and other aspects that showed nothing unusual except for the one previously undisclosed fact of the battery's expiry date.
It said that according to maintenance records, the battery on the beacon attached to the Flight Data Recorder expired in December 2012, but because of a computer data error it went unnoticed by maintenance crews. "There is some extra margin in the design to account for battery life variability and ensure that the unit will meet the minimum requirement," it said.
"However, once beyond the expiry date, the (battery's) effectiveness decreases so it may operate, for a reduced time period until it finally discharges," the report said. While it is possible the battery will operate past the expiry date, "it is not guaranteed that it will work or that it would meet the 30-day minimum requirement," said the report.
The report gave insight into flight Capt Zaharie Ahmad Shah's physical and mental well-being, saying he had no known history of apathy, anxiety or irritability. "There were no significant changes in his lifestyle, interpersonal conflict or family stresses," it said.
It also said there were "no behavioural signs of social isolation, change in habits or interest, self-neglect, drug or alcohol abuse" by the captain, his first officer and the cabin crew.
Financial checks also showed nothing abnormal about their gross monthly income and spending pattern. It said the captain held several bank accounts and two national trust funds. He had two houses and three vehicles, but there was no record of him having a life insurance policy.
The co-pilot, First Officer Fariq Abdul Hamid, had two saving accounts and a national trust fund account. He owned two cars and "spent money on the upkeep" of his cars. "He does not have much savings in his bank account. He has a life insurance policy," it said.
The report also said 221 kilograms of lithium ion batteries packed by Motorola Solutions in northern Penang state did not go through security screening at Penang airport. The shipment was inspected physically by the airline cargo personnel and went through customs inspection and clearance before it was sealed and left Penang a day before the flight. At the Kuala Lumpur airport, it was loaded onto the plane without any additional security screening.
The report said the batteries were not regulated as dangerous goods. There were 99 shipments of lithium ion batteries on Malaysia Airlines flights to Beijing from January to May last year, it added.
The report came as families of the 239 people who were on board the plane marked the anniversary of the Boeing 777's disappearance, vowing to never give up on the desperate search for wreckage and answers to what happened to their loved ones.
Voice 370, a support group for the relatives, hosted a "Day of Remembrance" at a shopping centre in Kuala Lumpur with songs, poems and prayers.
"It is important to highlight to the public that we still don't have any answers and that we must pursue the search," said Grace Subathirai Nathan, whose mother, Anne Daisy, was on the plane.
"The lack of answers and definitive proof - such as aircraft wreckage - has made this more difficult to bear," Malaysian Prime Minster Najib Razak said in a statement. "Together with our international partners, we have followed the little evidence that exists. Malaysia remains committed to the search, and hopeful that MH370 will be found."
Chinese Foreign Minister Wang Yi said his government would provide "all needed service to every next of kin" and help uphold their "legitimate and lawful rights and interests".
Most of the plane's passengers were Chinese.
"A year has passed, the plane has not been located, but the search effort will continue," Mr Wang told a news conference in Beijing. "Today must be a difficult day for the next of kin. Our hearts are with you."
Australian Prime Minister Tony Abbott later said the search for MH370 will not end if the scouring of the current search area comes up empty.
Prior to Mr Abbott's comments, it was unclear what would happen if searchers scouring a 60,000-square-kilometre (23,166-square-mile) swathe of the southern Indian Ocean off Australia's west coast did not find the plane, which disappeared on March 8, 2014. The search in that area is expected to end in May.
Mr Abbott told reporters in Sydney that the search "can't go on forever, but as long as there are reasonable leads, the search will go on".
He said if the current search is unsuccessful, "there's another 60,000 square kilometres that we intend to search and, as I said, we are reasonably confident of finding the plane."