One 'black box' recovered from crashed Indonesia jet

One black box from the crashed Lion Air jet has been recovered, the head of Indonesia's National Transportation Safety Committee said Thursday, which could be critical to establishing why the brand new plane fell out of the sky.

The devices record information about the speed, altitude and direction of the plane as well as flight crew conversations and could hold vital clues to the cause of the deadly accident.

"We found one of the black boxes," Soerjanto Tjahjono told AFP.

It was not clear whether it was the flight data recorder or cockpit voice recorder.

The Boeing-737 MAX 8, which went into service just a few months ago, plunged into the Java Sea off Indonesia's northern coast on Monday, killing 189 people, just 12 minutes after taking off from the capital Jakarta en route to Pangkal Pinang city.

The single-aisle Boeing plane is one of the world's newest and most advanced commercial passenger jets.

Images from the crash site showed two divers swim to a support vessel and place an orange-coloured device into a plastic tub.

Despite the name, black boxes are in fact bright orange with reflective stripes, and all commercial planes are obliged to have them on board.

They're built to survive at vast depths and in extreme heat, and are fitted with a beacon which can emit a signal for one month.

Black box data help explain nearly 90 percent of all crashes, according to aviation experts.

"Data from the plane -- the engine, all the instruments -- are recorded there," aviation analyst Dudi Sudibyo told AFP.

"If there is an anomaly, some technical problem, it is recorded there too."