A Lion Air jet that plunged into the sea last month, killing all 189 people aboard, should have been grounded over a technical problem on a trip prior to the fatal flight, Indonesia's transport safety agency have announced.
"During the flight From Denpasar to Jakarta, the plane was experiencing a technical problem but the pilot decided to continue the flight," Nurcahyo Utomo, aviation head at the National Transport Safety Committee, told reporters.
"In our opinion, the plane was no longer airworthy and it should not have continued" flying, he added.
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 preliminary safety report, published on Wednesday said Lion Air needed to improve its safety culture and better document all repair work carried out.
The Boeing 737 MAX vanished from radar about 13 minutes after taking off. Source: Flickr/Bathara Sakti
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.
The report also suggested the pilots struggled with the plane's anti-stall system as they radioed in a request to return to Jakarta's main airport.
The findings will heighten concerns there were problems with key systems in one of the world's newest and most advanced commercial passenger planes.
Investigators have previously said the doomed aircraft had problems with its airspeed indicator and angle of attack (AOA) sensors, prompting Boeing to issue a special bulletin telling operators what to do when they face the same situation.
An AOA sensor provides data about the angle at which air is passing over the wings and tells pilots how much lift a plane is getting. The information can be critical in preventing an aircraft from stalling.
Officials inspect the engine of the crashed Lion Air jet, following the fatal crash. Source: AAP
Dubious record
The Indonesian National Transportation Safety Committee has retrieved one of the plane's black boxes -- the flight data recorder -- but is yet to locate the cockpit voice recorder.
Black box data showed the plane had an airspeed indicator issue on multiple earlier flights, investigators said.
Lion must take steps "to improve the safety culture and to enable the pilot to make (a) proper decision to continue the flight," the safety agency said, adding that the carrier must ensure "all the operation documents are properly filled and documented".
Despite a dubious safety record and an avalanche of complaints over shoddy service, the budget carrier's parent Lion Air Group, which also operates Batik Air and Wings Air, has captured half the domestic market in less than 20 years of operation to become Southeast Asia's biggest airline.
Indonesia's aviation safety record has improved since its airlines, including national carrier Garuda, were subject to years-long bans from US and European airspace for safety violations, although the country has still recorded 40 fatal accidents over the past 15 years.
But Boeing has also come under fire for possible glitches on the 737 MAX - which entered service just last year.
Australian Federal Police take part in the investigation at the crash site of the wrecked Garuda Boeing 737 plane at Adisucipto airport in Yogyakarta in 2007. Source: EPA
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.
"I am really surprised if Boeing has not shared all the flight performance parameters with pilots, unions, and training organisations," University of Leeds aviation expert Stephen Wright told AFP before the report was released.
"I cannot forsee why a manufacturer would not incorporate potential known problems into their mandatory training programs," he said, adding that "a deliberate omission would have serious legal ramifications"
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.
Lion Air Flight JT610 plunged into the sea less than half an hour after taking off on a routine flight to Pangkal Pinang city.
Authorities have called off the grim task of identifying victims of the crash, with 125 passengers officially recognised after testing on human remains that filled some 200 body bags.
