JAKARTA - The Lion Air plane that crashed just minutes after take-off last month should have been grounded after experiencing "serious problems" on its penultimate flight from Bali to Jakarta, said Indonesia's National Transport Safety Committee (KNKT).

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.

Mr Nurcahyo said on Wednesday (Nov 28) that the Boeing 737 Max 8 had been dogged by problems on several earlier flights. Investigators had previously found that on previous flights, the plane had issues with airspeed and altitude readings.

Aircraft maintenance logs show that, since Oct 26, there had been six reports of faulty equipment. But each time, the problem was indicated to be rectified, Mr Nurcahyo told reporters at a press conference on the commitee's preliminary report on downed Lion Air Flight JT610.

The plane bound for Pangkal Pinang from Jakarta crashed just minutes after take-off on Oct 29, killing all 189 people on board, making it the country's second deadliest air crash.

Barely seven hours before the ill-fated flight, the jet had made a rocky trip from Bali to Jakarta, as Flight JT43. There was a difference between readings on the side of the pilot and that of the co-pilot for the angle of attack - the angle at which wind is passing over the wing.

KNKT also recommended that Lion Air improve its safety culture.

While it acknowledged that Lion Air, along with other bodies like Boeing, have taken safety actions since the crash, the low-cost carrier can do more. For one, Lion Air should make sure its pilots are able to make proper decisions should issues emerge during a flight, said KNKT.

Its preliminary report does not fully unravel the mystery behind the crash. That will take longer - KNKT plans to finish a complete study within 12 months of the accident.

"This is a report of facts. There is no analysis or conclusion as not all facts have been collected," said Mr Nurcahyo about the preliminary findings.

KNKT plans, among other things, to conduct aircraft simulator exercises, in the Boeing engineering simulator in the US.

"The investigation is continuing and, should any further relevant safety issues emerge during the course of the investigation, KNKT will immediately bring the issues to the relevant parties and publish as required," said Mr Nurcahyo.

He told Parliament last week that flight recorder data showed that the pilot had fought till the end, as the plane nose-dived to the ground.

Data from the flight recorder - which was retrieved just days after the crash, and contains 69 hours of information from its last 19 flights - showed that the plane had experienced technical difficulties soon after take-off, with the pilot and co-pilot receiving different airspeed readings.

The jet, added Mr Nurcahyo, had experienced "the same challenges" on its penultimate flight the previous night from Bali to Jakarta. The pilot that flight had, however, managed to keep control of the plane.

As JT610 began to nosedive, the pilot attempted to offset this to keep the plane in the air - but this became "increasingly difficult", said Mr Nurcahyo. The plane then "dropped", crashing into the sea at a speed of more than 400 mph.

KNKT will press on with efforts to retrieve the cockpit voice recorder, with local newspaper Kompas reporting on Tuesday that the commission is looking for a suitable ship. Among other things, the ship should have a crane powerful enough to lift large aircraft parts, and should be able to maintain its position without an anchor, as the crash site is close to a Pertamina fuel pipe.

"We hope to get a ship soon, so we can carry out the search for the cockpit voice recorder this week," said Mr Nurcahyo Utomo, the KNKT sub-committee head for air accidents. "We will do our utmost to get all the items and information we need to investigate."

Indonesia had on Nov 23 wrapped up the task of identifying crash victims from recovered body parts. The police's disaster victim identification team managed to identify 125 of the 189 victims from human remains that filled about 200 body bags.