Indonesian authorities on Wednesday said that flight carrier Lion Air must improve its safety culture and work better to document repair work on its planes, AFP reported. The findings were part of a preliminary report prepared by investigators looking into what caused a Boeing 737 Max passenger jet to crash minutes after takeoff on October 29.

All 189 people on board Lion Air flight JT 610, from Denpasar to Jakarta, were killed when it crashed into the Java Sea.

With a final crash report likely to be filed next year, the Indonesian transport safety agency has not set out a definitive cause of the accident. However, the investigators blamed Lion Air for putting the plane back into service despite having failed to fix a problem with the airspeed indicator in the days leading up to the October 29 flight.

Lion Air must take steps “to improve the safety culture and to enable the pilot to make [a] proper decision to continue the flight”, said the safety agency. It added that the carrier must ensure “all the operation documents are properly filled and documented”.

The report also suggested that the pilots struggled with the plane’s anti-stall system as the crew experienced multiple malfunctions after takeoff. These warnings continued for 11 minutes until the plane crashed into the sea. While authorities were able to locate the flight data recorder, they are still searching for the cockpit voice recorder.

The findings indicate that the pilots struggled to keep the plane steady as its nose tilted dangerously downward more than two dozen times, The New York Times reported. The pilots managed to pull the nose back up continuously until they finally lost control of the plane.

“The pilots fought continuously until the end of the flight,” said Captain Nurcahyo Utomo, chief of the air accident subcommittee of the Indonesian National Transportation Safety Committee, which is leading the investigation.

Authorities had earlier said that one of the “angle of attack” sensors on the aircraft had provided faulty data and the plane had experienced problems with its airspeed indicators on its last four flights. The “angle of attack” sensor helps the plane’s computers understand if the aircraft is stable.