A preliminary report by Indonesia's national transport safety committee (NTSC) said that the plane was not airworthy on its previous flight and should not have been cleared to fly after earlier crews experienced similar problems. The plane crashed just 15 minutes after the flight took off from Jakarta on October 29, with the system showing it dipped up and down more than 26 times during that brief period.
A report based on black box data from an Indonesian Lion Air jet that crashed last month cites equipment failures and the airline's safety measures as factors in the disaster.
At the news conference Wednesday, Utomo said that the plane, in both the doomed flight and the previous flight from Bali to Jakarta, had experienced a stick shaker - "a warning that showed that the plane was going to stall", he said.
Tjahjono said that due to the small size of the debris found and loss of the plane's engine blades, investigators determined that Flight 610 did not explode in the air, but was in "good shape" before it crashed 13 minutes after takeoff.
An artist's conception shows the Boeing 737 MAX 8 jet.
Aviation expert Geoffrey Thomas called the report "very comprehensive" and said that he could not understand why Lion Air had deemed the plane suitable for service.
It is unclear why the pilots did not employ procedures to disable the automated system.
Investigators had previously revealed that the plane, on previous flights, had experienced technical problems related to airspeed and altitude readings. To prevent a stall, the automated anti-stall system directed the aircraft's nose down.
They also asked Lion Air to update its operational manuals in order to improve the airline's "safety culture".
Boeing says the procedure for dealing with a so-called runaway stabilizer, under which anti-stall systems push the nose down even when the plane is not entering a stall or losing lift, had not changed between earlier version of the 737 and the newly delivered 737 MAX.More news: Kawhi Leonard Responds To Gregg Popovich's "He Wasn't A Leader" Remark
From nearly the moment it took off, "the pilots fought continuously until the end of the flight", says an official with the crash investigation.
In response to initial findings from the jet's flight data recorder, Boeing issued a bulletin to airlines reiterating procedures and advising them to add information on MCAS to flight manuals, which was followed by a US Federal Aviation Administration directive making that mandatory. The captain's stick shaker activated shortly after takeoff and remained nearly continuously active.
"We haven't found the information in the manual relevant to the new feature to the 737- MAX, related to the feature for the stall prevention system", he said.
Boeing said that action was part of well-established protocols for all 737s.
The captain of that flight declared a "PAN PAN", one step below and emergency and landed the plane safely.
Indonesian investigators determine the downed 737 jet was "not airworthy"; Greg Palkot reports on the findings.
The parents of one passenger is suing Boeing, alleging the 737 MAX 8 had an unsafe design.
Indonesia's aviation safety record has improved since its airlines, including national carrier Garuda, were subject to years-long bans from United States and European airspace for safety violations, although it has still recorded 40 fatal accidents over the past 15 years.
Boeing said Tuesday that it "continues to work closely with the U.S. National Transportation Safety Board as technical advisers to support the ongoing investigation" by the Indonesian authorities.