Indonesian investigators have said the Lion Air plane that crashed last month killing 189 people was not airworthy and should have been grounded.
The Boeing 737 Max plane crashed into the Java Sea shortly after departing Jakarta on 29 October.
A preliminary report has found technical problems had been reported on previous flights.
The 737 Max is a new version of Boeing's original 737 and has become its fastest selling plane.
The preliminary report details what is known by authorities about the short time the plane was in the air, but investigators said it does not give a definitive cause for the accident.
What's in the report?
The findings by the National Transport Safety Committee (KNKT) suggest that Lion Air put the plane back into service despite it having had problems on earlier flights.
Its previous flight was from Denpasar in Bali to Jakarta.
“During [that] flight, the plane was experiencing a technical problem but the pilot decided to continue,” Nurcahyo Utomo, aviation head at the National Transport Safety Committee, told reporters.
The report outlines several maintenance procedures that were carried out in response to those problems.
“In our opinion, the plane was no longer airworthy and it should not have continued,” he said. The committee report itself, though, does not spell out that conclusion.
The report also indicated that pilots struggled with the aircraft's anti-stall automated system - a new feature in the 737 Max families.
The report says the airline should ensure the operations manual is followed "in order to improve the safety culture and to enable the pilot to make [a] proper decision to continue the flight".
It also says the carrier must ensure “all operations documents are properly filled and documented.”
How did the crash unfold?
The plane was making a one-hour journey to the western city of Pangkal Pinang when it went down.
The jet crashed following a request from the pilot for permission to turn back to the airport minutes after taking off from Jakarta.
Investigators had previously revealed that the plane, on previous flights, had experienced technical problems related to airspeed and altitude readings.
Therefore the ‘angle-of-attack’ sensor, which contributes to those readings, had been changed the day before the crash.
However, media reports have suggested the sensor malfunctioned on the ill-fated flight as well, forcing the nose of the aircraft downwards.
It is unclear why the pilots did not employ procedures to disable the automated system.
The plane's flight data recorder has been retrieved but authorities are yet to locate the cockpit voice recorder which could provide more information about how the pilots reacted.
Victims' families are suing Boeing over alleged faults with the jet's design, focusing on the automated safety feature.
'We want to understand who is responsible'
Rebecca Henschke, BBC Indonesia editor, Jakarta
Rini Soegiyono's sister and brother-in-law were on the flight. After hearing the preliminary findings, she said she had mixed emotions.
“Sad, grieving, mourning, angry and disappointed - these are all the words that describe how I am feeling. But I am trying to be objective and strong.”
She, like many grieving families, is mostly frustrated that the search for the remaining passengers has officially ended.
“There are still 64 families who haven't had their loved ones' remains identified and we have had to really push to get Lion Air and the authorities to search again for them. It's not good enough.”
They want the airline to fund a search to find the remaining passengers as well as the cockpit voice recorder that hasn't been retrieved. It will be key, she says, to understand what went wrong.
“We are watching and waiting to understand who is responsible. I know the world is also watching. It's important to know so it will not happen again. We don't want any family to have to go through what we are going through.”
Indonesia's air safety record
Budget airline Lion Air has in recent years risen to become a major player in South East Asia's low-cost aviation sector.
The airline, which also operates Batik Air and Wings Air, has a dubious safety record, though, and has had more accidents than other airlines in the country.
Overall, Indonesia's aviation safety record has improved a lot since the days when even its national carrier Garuda was blacklisted from European and US airports over safety concerns.