The black box voice recorder from a Lion Air flight which crashed off the coast of Jakarta in October has been found by Indonesian officials.
All 189 people on board died when Flight JT610 plunged into the sea shortly after taking off for the short flight to Pangkal Pinang.
The pilot had asked air traffic control for permission to turn back to the airport but then contact was lost.
Investigators say the aircraft had encountered technical problems.
The main body of the Boeing 737 MAX has never been found.
Indonesian navy spokesman Agung Nugroho told Reuters that the cockpit voice recorder was found 26ft under mud on the sea floor.
A weak signal from the recorder had been detected “for several days”.
He added that the recorder had “obvious scratches on it”, but that it was unclear what damage it had suffered.
Listening to the last conversations between the pilots and ground control should help investigators to finish piecing together what went wrong in the short flight.
The first black box, the aircraft’s flight data recorder, was found last November, buried in debris on the floor of the Java Sea.
Officials had said then that it could take up to six months to analyse data from the black boxes.
Findings by Indonesia’s transport safety committee (KNKT) now suggest that Lion Air had put the aircraft back into service despite it having had problems on earlier flights, the BBC reported.
The pilots appeared to struggle with an automated system designed to keep the plane from stalling – a new feature of the Boeing 737 MAX.
The anti-stalling system repeatedly forced the nose down, despite efforts by pilots to correct this.
Investigators have now said that the aircraft was not airworthy, and should have been grounded.