Searchers have recovered plane parts and human remains from an area between Lancang and Laki islands in the Thousand Island chain, just north of Jakarta. The flight data recorder tracked hundreds of parameters showing how the plane was being operated.
Most retrieval efforts ended about two weeks after the crash, but a limited search is continuing for the missing memory unit of the cockpit voice recorder, which apparently broke away from other parts of the device during the crash.
The bright orange voice recorder was taken to Jakarta and given to the National Transport Safety Committee (KNKT), which is overseeing the accident investigation.
"We hope the KNKT could share information about what is contained in this VCR to improve our aviation safety," Sumadi said, referring to Indonesian acronym for the transport committee.
The KNKT chairman, Soerjanto Tjahjono, said the device will be taken to the investigators' "black box" facility. It will take five to seven days to dry and clean the device and to download its data, he said.
"Without the CVR ... it would be difficult to determine the cause of the plane crash," Tjahjono said, "We would disclose it transparently to avoid similar accidents in the future."
Rear Admiral Abdul Rasyid Kacong, the Navy's western region fleet commander, said the voice recorder was buried under 1m of seabed mud at a depth of 23m. Divers removed debris and carried out "desludging" operations to reach the recorder, he said.
Data from a preliminary investigation report, which didn't state any conclusions, showed the plane's left engine's throttle lever moved backwards on its own while the autopilot was engaged, reducing the power output of that engine before the jet plunged into the sea.
That report provided new details on persistent problems with an autothrottle on the 737-500 Sriwijaya Air jet and the airline's efforts to fix them. An autothrottle can be used by pilots to set the speed automatically, thereby reducing workload and wear on the engines.
It also might help answer questions for those who lost people in the disaster.
"I warmly welcome the CVR finding ... this is some relief from our despair," said Rafik Yusuf Alaydrus, whose wife, Panca Widia Nursanti, a teacher, died in the crash.
"We hope this could answer what caused the crash, especially for us who lost our loved ones," he said.
The 26-year-old jet had been out of service for almost nine months because of flight cutbacks due to the pandemic before resuming commercial flights in December.
The disaster has reignited concerns about safety in the aviation industry, which has grown quickly along with the economy since the fall of dictator Suharto in the late 1990s.
The United States banned Indonesian carriers from operating in the country in 2007 but lifted that restriction in 2016, citing improved compliance with international aviation standards. The European Union lifted a similar ban in 2018.
Sriwijaya Air had had only minor safety incidents in the past, though a farmer was killed in 2008 when a plane went off the runway while landing due to a hydraulic issue.
In 2018, a Boeing 737 MAX 8 jet operated by Lion Air crashed shortly after taking off from the airport in Jakarta, killing 189 people. An automated flight-control system played a role in that crash, but the Sriwijaya Air jet did not have that system.
