Ship finds crashed AirAsia jet's fuselage at bottom of Java Sea

An Airbus investigator walks near part of the tail of the AirAsia QZ8501 passenger plane in Kumai Port, near Pangkalan Bun, Central Kalimantan January 12, 2015. Flight QZ8501 vanished from radar screens over the northern Java Sea on December 28, 2014 less than half-way into a two-hour flight from Indonesia's second-biggest city of Surabaya to Singapore. [Photo/Agencies]

The so-called black boxes - which are actually orange - contain a wealth of data that will be crucial for investigators piecing together the sequence of events that led to the plane plunging into the sea.

The flight data recorder took only 15 minutes to download, but investigators will now need to analyse up to 25 hours of data and several thousand flight parameters covering things such as flying speed, altitude, fuel consumption, air pressure changes and inputs to the aircrafts controls.

"We are feeling relieved but there is still a lot of work ahead of us to analyse it," said Siswosuwarno.

Investigators were also expected on Wednesday to begin downloading data from the cockpit voice recorder, which retains the last two hours of conversations on the flight deck and between the pilots and air traffic controllers.

As is standard procedure, the NTSC will file a preliminary report, which will be made public, to the International Civil Aviation Organization within 30 days. A final report on the crash is not expected to be published for at least a year, Siswosuwarno said.

After the recovery of the two black boxes, Indonesia is expected to scale back search and rescue operations in the Java Sea.

But government officials sought to reassure victims' families that efforts to retrieve the remains of their loved ones would continue.

"We understand if the search becomes smaller ... but the bodies have to be found," said Frangky Chandry, whose younger brother was on the plane.

"We want to bury our family. That's what we want."