On October 29, 2018, Lion Air Flight 610, a Boeing 737 MAX 8 flying a domestic route from Jakarta to Pangkal Pinang, plunged into the Java Sea off Karawang some thirteen minutes after takeoff. All 189 people aboard — 181 passengers and 8 crew — were killed.
The angle-of-attack sensor on the captain’s side of the aircraft had been replaced the day before, during a stop in Bali, and was miscalibrated. Its false readings repeatedly triggered the 737 MAX’s MCAS flight-control system, which pushed the aircraft’s nose down again and again. The pilots did not know the system existed: MCAS had not been described in the flight crew manuals, and no training on it was required. The crew fought the system through repeated cycles before losing control.
The same fault had appeared on the aircraft’s previous flight the night before. That crew, helped by an off-duty pilot riding in the cockpit, had recognized the runaway stabilizer trim and landed safely in Jakarta — but the defect was not repaired before Flight 610 departed.
Indonesia’s National Transportation Safety Committee (KNKT) issued its final report (KNKT.18.10.35.04) on October 25, 2019. It listed nine contributing factors, among them an MCAS design that relied on a single angle-of-attack sensor, the absence of MCAS from pilot documentation and training, the miscalibrated replacement sensor, incomplete maintenance records, and shortcomings in the crew’s handling of the emergency.
After a second 737 MAX crash in Ethiopia in March 2019, the type was grounded worldwide for twenty months. MCAS was redesigned to compare both angle-of-attack sensors and to limit its authority, pilot training was revised, and the accidents drove major reforms of aircraft certification oversight in the United States and abroad.
Download the KNKT Final Report (12.9 MB file)