The New York Times is reporting a harrowing breakthrough in the investigation into the crash of the Lion Air Boeing 737 Max 8 that fell into the Java Sea in October, killing all 189 people on board.

Flight data taken from a recovered black box prepared by Indonesian air crash investigators for release on Wednesday, was reviewed by The New York Times.

The data reveal how hard the two pilots battled to stay in the air and the difficulties they faced in dealing with what may have been a rogue automated system. The data are also consistent with the investigator’s main lead that the Boeing system installed on its latest generation of 737s to prevent the plane’s nose from getting too high and causing a stall actually forced the nose down because of incorrect data sent from sensors on the fuselage.

They further found that Lion Air must improve its safety culture and better document repair work on its planes.

The flight from Bali to Jakarta on 28 October had experienced similar technical issues to the doomed flight the next day from Jakarta to Pangkal Pinang, said Nurcahyo Utomo, head of Indonesia’s national transport safety committee (KNKT).

The Boeing 737 MAX vanished from radar about 13 minutes after taking off from Jakarta on October 29, slamming into the Java Sea moments after it had asked to return to the capital.

The transport safety agency did not pinpoint a definitive cause of the accident, with a final crash report not likely to be filed until next year.

But its investigators said that Lion Air kept putting the plane back into service despite repeatedly failing to fix a problem with the airspeed indicator in the days leading up to the fatal flight.

Mr Nurcahyo Utomo, the KNKT sub-committee head for air accidents, said: “In our opinion, the plane was not airworthy.”

Lion Air had insisted after the crash that the plane – which was manufactured in 2018, and only in operation since Aug 15 – was airworthy.

Boeing has also come under fire for possible glitches on the 737 MAX – which entered service just last year.

The APA, a US airline pilots union, said that carriers and pilots had not been informed by Boeing of certain changes in the aircraft control system installed on the new MAX variants of the 737.

Several relatives of the crash victims have already filed lawsuits against Boeing, including the family of a young doctor who was to have married his high school sweetheart this month.