A series of failures led to the crash of a Lion Air flight, which killed 189 people and led to the grounding of the Boeing 737 Max, a report has found. Investigators said faults by Boeing, Lion Air and pilots caused the crash, report agencies.
Five months after the disaster in October last year, an Ethiopian Airlines plane crashed, killing all 157 people on board, which led to the grounding of the entire 737 Max fleet.
Faults with the plane's design have been linked to both crashes.
On Friday, air crash investigators in Indonesia released their final report, detailing the list of events that caused the Lion Air jet to plunge into the Java Sea. "From what we know, there are nine things that contributed to this accident," Indonesian air accident investigator Nurcahyo Utomo told reporters at a news conference.
"If one of the nine hadn't occurred, maybe the accident wouldn't have occurred." The 353-page report found the jet should have been grounded before departing on the fatal flight because of an earlier cockpit issue.
However, because the issue was not recorded properly the plane was allowed to take off without the fault being fixed, it said.
Further, a crucial sensor - which had been bought from a repair shop in Florida - had not been properly tested, the report found. On Friday, the US aviation regulator revoked the company's certification.
The sensor fed information to the plane's Manoeuvring Characteristics Augmentation System - or MCAS. That software, which is designed to help prevent the 737 Max from stalling, has been a focus for investigators trying to find the cause of both the Lion Air and Ethiopian Airlines crashes.
Indonesian investigators identified issues with the system, which repeatedly pushed the plane's nose down, leaving pilots fighting for control.
It showed there were incorrect assumptions about how the MCAS control system would behave and that the "deficiencies" had been highlighted during training.
Further, the report found that the first officer, who had performed poorly in training, struggled to run through a list of procedures that he should have had memorised.
He was flying the plane just before it entered into the fatal dive, but the report said the captain had not briefed him properly when he handed over the controls as they struggled to keep the plane in the air.
The report also found that 31 pages were missing from the plane's maintenance log. Indonesian investigators have previously said mechanical and design problems were key factors in the crash of the Lion Air plane.
