(CNN) – Investigators have found no indications of unusual behavior among the pilots and cabin crew of Malaysia Airlines Flight 370 before it took off and vanished a year ago.
“There were no behavioral signs of social isolation, change in habits or interest, self-neglect, drug or alcohol abuse of the captain, first officer and the cabin crew,” said an interim report released Sunday about the investigation into the passenger jet’s mysterious disappearance.
The report, which contained factual information about the missing plane rather than analysis, offered relatives of the 239 people on board no apparent answers about why the aircraft dropped off radar.
It said MH370’s captain, Zaharie Ahmad Shah, didn’t have any personal or financial problems that would cast suspicion on him.
“The captain’s ability to handle stress at work and home was good. There was no known history of apathy, anxiety, or irritability,” the report said. “There were no significant changes in his lifestyle, interpersonal conflict or family stresses.”
Investigators looked into the backgrounds of the different crew members. They also examined closed-circuit TV footage of the flight crew at airports on at least three previous flights and saw no signs of change in behavior.
Expired battery on beacon
The interim report, which Malaysian authorities were required to release under international civil aviation standards, revealed that the battery of the underwater locator beacon on MH370’s flight data recorder expired more than a year before the plane’s disappearance.
The report, citing maintenance records, said that there was no evidence to suggest the battery was replaced before its expiry in December 2012. While such a battery can operate past its expiry date, it said, “it is not guaranteed that it will work or that it would meet the 30-day minimum requirement.”
The battery on the plane’s other so-called black box, the cockpit voice recorder, was replaced as scheduled and remained within its expiry date, the report said.
Investigators interviewed maintenance staff and found that the computerized replacement schedule had not been updated correctly when the flight data recorder, and its locator beacon were replaced in February 2008.
The mistake was not discovered until after MH370’s disappearance, the report said, and Malaysia Airlines subsequently checked its entire fleet of planes to make sure there were no other oversights.
‘No words can describe the pain’
As family members of the missing passengers and crew members gathered Sunday to remember their loved ones, the Malaysian government said it remains committed to the search for the plane.
One year later, what happened to MH370?
One year later, what happened to MH370? 03:03
“No words can describe the pain the families of those on board are going through,” Malaysian Prime Minister Najib Razak said in a statement. “The lack of answers and definitive proof — such as aircraft wreckage — has made this more difficult to bear.
“Together with our international partners, we have followed the little evidence that exists,” Najib said. “Malaysia remains committed to the search, and hopeful that MH370 will be found.”
Indian Ocean search
Investigators have so far failed to explain why Flight 370 veered wildly off its scheduled route from Kuala Lumpur, Malaysia, to Beijing in the early hours of March 8, 2014.
Malaysia: We hope to complete MH370 search by May
Malaysia: We hope to complete MH370 search by May 03:27
Officials say that expert analysis of radar and satellite data indicates that the Boeing 777 eventually went down in the southern Indian Ocean.
A group of ships with specialized equipment is searching for traces of the passenger jet in the vast depths of a remote area of ocean where experts believe MH370 most likely ended up.
Those efforts are expected to be completed in May. It is unclear what will happen if search teams complete their current mission without finding any sign of the plane.
Families demand answers
The absence of tangible evidence of what happened to the plane and the people on board has tortured family members and spawned a host of speculative theories.
Wife of MH370 victim: I see him everywhere
Wife of MH370 victim: I see him everywhere 03:14
Relatives have expressed dissatisfaction and anger over the information they’ve been given and repeatedly demanded more from government and airline officials — but with little success.
For many of them, the Malaysian government’s decision in late January to officially declare the loss of MH370 an accident, enabling the insurance payout process to begin, felt premature.
‘We will never forget them’
On Sunday, about 500 employees of Malaysia Airlines gathered at a private event in Kuala Lumpur to honor their 13 colleagues who were on Flight 370, the airline said.
MH370: Families reflect one year later
MH370: Families reflect one year later 02:20
“We miss them and we will never forget them. They will always remain in our hearts,” Malaysia Airlines Chairman Mohamad Nor Yusof told the gathering, according to the airline.
Between 200 and 300 people gathered at a public commemoration at a mall in Kuala Lumpur. Family members of about 20 passengers aboard the plane attended the event, which involved songs, poetry reading and the signing of a petition urging the Malaysian government to continue the search.
Most of the passengers on Flight 370 were Chinese. But in Beijing, paying respects to missing loved ones proved difficult. A heavy police presence at a temple intimidated some relatives of passengers who had gone there to honor their family members.
CNN’s Pamela Boykoff, Brian Walker, David McKenzie and Sarita Harilela, and journalist Chan Kok Leong contributed to this report.