On 29 October 2018, the Boeing 737 MAX 8 operating the route, carrying 181 passengers and 8 crew members, crashed into the Java Sea 13 minutes after takeoff, killing all 189 occupants on board.

The subsequent investigation, led by the National Transportation Safety Committee (NTSC), revealed that a new software function in the flight control system caused the aircraft to nose down.

That function, the Maneuvering Characteristics Augmentation System (MCAS), had been intentionally omitted by Boeing from aircraft documentation for aircrews, so the Lion Air pilots did not know about it nor know what it could do.

Investigators concluded that an external device on the aircraft, the angle-of-attack (AoA) sensor, was miscalibrated due to improper maintenance which sent erroneous data to MCAS.

The pilots did not properly follow the checklist, with the result that MCAS remained active and repeatedly put the aircraft into an unsafe nose-down position until it crashed into the water.

These training advisories were not fully followed, however, and similar issues caused the crash of Ethiopian Airlines Flight 302 on 10 March 2019, prompting a worldwide grounding of all 737 MAX aircraft.

The final report by the National Transportation Safety Committee (NTSC) of Indonesia criticized Boeing's design and the FAA's certification process for MCAS and said the issues were compounded by maintenance issues and lapses by Lion Air’s repair crews and its pilots, as well as Xtra Aerospace, a US-based company that supplied Lion Air with the AoA sensor.

[48][needs update] The speaker of the People's Representative Council, Bambang Soesatyo, later asked the government to enforce stricter rules for the aviation industry and to audit every airliner in the country.

Indonesian President Joko Widodo, who was attending a conference in Bali during the crash,[55] visited the recovery efforts at the Port of Tanjung Priok the next day.

[58][59][needs update] The government-owned social insurance company Jasa Raharja announced that the victims' families would each receive 50 million rupiah (US$3495) in compensation.

[61] Chairman of Indonesia's Alliance of Independent Journalists (AJI), Abdul Manan, stated that images of debris were broadcast repeatedly and inappropriately.

[62] On 31 October, Transportation Minister Budi Karya Sumadi temporarily suspended Lion Air's technical director Muhammad Arif from his duties based on the crash investigation.

[68] Air Marshal Muhammad Syaugi, head of Basarnas, suggested that most of the victims were still inside the fuselage, as in the days following the crash rescue personnel only managed to recover a small number of body parts.

[75] On 31 October, acoustic "pings" were reported to have been detected, no further than 3 km (1.6 nmi; 1.9 mi) from the group of eight current search points, which were possibly from one of the underwater locator beacons (ULBs) attached to the aircraft's flight recorders.

[13]: 243 [102][103] Divers detected a signal from an underwater locator beacon coming from underneath the aircraft wreckage and were able to fix the approximate position of the CVR, but did not succeed in recovering it.

[106][107][108] The Lion Air aircraft flight recorders were retrieved with assistance from Singapore's Transport Safety Investigation Bureau, which sent on 29 October 2018, three specialists and an underwater locator beacon detector to help recover the devices.

[128][129] On 5 November, the NTSC announced that Flight 610 was still intact when it crashed into the sea at high speed, citing the relatively small size of the pieces of debris.

[137] Shortly after takeoff on 29 October, issues involving altitude and airspeed continued due to erroneous AoA data and commanded automatic nose-down trim via the MCAS.

[137] Leeham News, which principally covers Airbus, Boeing, Bombardier, and Embraer issues,[138] reported that the crew did not have a clear knowledge that trim runaway checklist will disengage MCAS.

During the design and certification of the Boeing 737-8 (MAX), assumptions were made about flight-crew response to malfunctions that, even though consistent with current industry guidelines, turned out to be incorrect.

Based on the incorrect assumptions about flight-crew response and an incomplete review of associated multiple flight deck effects, MCAS's reliance on a single sensor was deemed appropriate and met all certification requirements.

This was caused by the difficulty of the situation and performance in manual handling, NNC execution, and flight-crew communication, leading to ineffective CRM application and workload management.

The NTSC recommended that Lion Air improve the duration and content of its safety management system training, including the identification of equipment hazards, such as the continuous stick shaker and trim runaway, which the pilot on the previous flight did not report.

[150] On 7 November, on the basis of preliminary information gathered in the investigation of the Lion Air accident, the US FAA issued an emergency airworthiness directive requiring that amended operating limitations and procedures relating to erroneous data from an AoA sensor be inserted into the aircraft flight manual of each 737 MAX aircraft,[151][152] and urged all airlines operating Boeing 737 MAX 8s to heed the warnings.

[153] On 25 October 2019, after the release of the Final Report by NTSC, the FAA revoked the repair certification of Florida-based Xtra Aerospace LLC, which fixed an AoA sensor suspected of contributing to the crash.

[157] The Wall Street Journal reported that Boeing had "decided against disclosing more details to cockpit crews due to concerns about inundating average pilots with too much information.

"[159] The association's United Airlines branch, in line with its management, disagreed as the 737 pilot manual includes a standard procedure to shut down the flight-control behavior, and dismissed the MCAS implication in the accident as "speculation" based on the Boeing safety-warning bulletin and the follow-on FAA airworthiness directive.

[160] In an internal message on 19 November 2018, Boeing CEO Dennis Muilenburg defended the flight-crew operations manual as describing the relevant function of MCAS.

[170] In December 2020, a federal judge in Chicago froze the assets of attorney Thomas Girardi, as "finding that he misappropriated at least US$2 million in client funds that were due to the families of those killed in the crash".

[173] On 10 March 2019, another 737 MAX 8, operated by Ethiopian Airlines (registration ET-AVJ), crashed shortly after takeoff from Addis Ababa; all 157 people on board perished.