Indonesian Navy divers retrieved the black boxes of the Sriwijaya Air Boeing Co. jet that plunged into the Java Sea shortly after take-off from Jakarta on Saturday afternoon, a key step in discovering what caused the aircraft carrying 62 people to crash.

Black boxes are crucial to understanding what happened as they capture sound in the cockpit and monitor flight data. The aircraft in this instance was a nearly 27-year-old Boeing 737-500, not the much newer 737 just emerging from a 20-month worldwide grounding after two crashes, including a Lion Air flight in October 2018 that also plummeted into Indonesia’s Java Sea.

Search teams retrieved the black boxes on Tuesday, according to the Associated Press, which didn’t cite sources. Their locator beacons were detected soon after the crash, but efforts to collect the flight recorders were hampered by muddy waters and debris from the jet scattered in the sea.

Indonesia is one of the world’s fastest-growing aviation markets, but also has one of the worst safety records. The country’s planes were barred by the European Union in 2007 over safety concerns. The ban wasn’t fully lifted until 2018.

The black boxes will provide more information on what caused the plane to plunge more than 10,000 feet in a matter of seconds. Both pilots in command of Sriwijaya Air Flight 182 were experienced and the airline has a solid safety record, with no fatal accidents since it was founded in 2003. The plane itself also had a good safety record.

Representatives from Boeing and the U.S. National Transportation Safety Board will leave for Jakarta this week to help with the investigation, a person familiar with the matter said, asking not to be named because the matter is private. The Indonesian government has granted them a waiver to enter the country during its coronavirus-related travel ban.

Human remains collected from the crash site have been handed over for identification, along with 30 bags containing parts of the plane, search and rescue operation director Rasman MS said at a briefing Tuesday. One victim was identified as 29-year-old Okky Bisma. Seven children and three infants were among the passengers.

Flight 182 was delayed for 56 minutes in Jakarta, according to FlightRadar24, as heavy rain lashed the Indonesian capital. Soekarno-Hatta International Airport’s official weather report about 10 minutes before the crash said there was light rain with a cloud ceiling starting at 1,800 feet. Weather has been a factor in several crashes in Indonesia.

Preliminary data appear to show the pilots were possibly disoriented, at least partly because of the bad weather, aviation analyst Gerry Soejatman said. Teal Group’s Richard Aboulafia said the cause was unlikely to be an aircraft design flaw given the long service of the 737-500.

Sriwijaya Air started out as a carrier with just one Boeing 737-200, flying short routes from Jakarta. It now flies across the Indonesian archipelago as well as internationally to Timor-Leste and Penang in Malaysia. Flight 182 was headed to Pontianak on the island of Borneo.

Indonesia’s flag carrier PT Garuda Indonesia briefly took over Sriwijaya Air’s operations and those of its unit NAM Air in 2018 as the airline restructured its debt. Garuda also conducted maintenance then, which is now carried out by engineers from Indonesia and overseas.

Indonesia, with a population of about 270 million people spread over thousands of islands, is the world’s fifth-biggest aviation market in terms of scheduled capacity, according to OAG Aviation Worldwide. The coronavirus pandemic has squeezed the country’s airlines, as it has with others around the world, and domestic seat capacity is still 32% below pre-covid levels, OAG said.