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Cases / REG-0009

Boeing 737 MAX MCAS: a flight-control function acts on a single sensor, repeatedly and without pilot command; Lion Air 610 (29 Oct 2018) and Ethiopian 302 (10 Mar 2019)

Ended in harmMachines · Air and seaHuman supervisesProduction
REG-0009Updated 2026-10-2812 sources, 12 linkedPublic regulatory

What happened

On Lion Air 610 and Ethiopian 302, the Boeing 737 MAX's MCAS function acted on erroneous data from a single angle-of-attack sensor and repeatedly commanded nose-down trim the crews could not sustainably counter, and 346 people died. On the record, MCAS could activate without two sensors agreeing, and pilots were largely unaware it existed. The MAX was grounded, and Boeing entered a deferred prosecution agreement of about $2.5 billion.

A plain summary of the typed record below; where they differ, the record governs.

Verification: 6 of 6 checks complete
✓ Structured and checkedevery claim typed and sourced, then checked by the Register's automated checker for missing sources and mistyped claims
✓ Sources linked12 of 12 sources link to the record (12 to a primary record)
✓ Sources checked claim by claimevery claim checked against its source on 2026-10-22
✓ Interpretation checked statement by statementeach statement of the Register's interpretation checked against a source on 2026-10-21
✓ Reviewed by the editorreviewed 2026-10-28
✓ Reply offeredBoeing: offered
Corrections · 31, latest 2026-10-21

Changes to what this case says, with the reason. Every earlier version is kept.

  • 2026-10-21: Inference: value. Found in the editor's second, independent check of the interpretations, 21 october 2026: third check: the court found boeing concealed mcas's expansion to low speeds, not mcas itself, from the group that set pilot training, and the families' standing is as representatives of crime victims (ecf no. 116, pdf pages 2 to 4 and 11 to 14).
    Show the change
    Before: Before the Lion Air crash, the pilots supervising the Maneuvering Characteristics Augmentation System (MCAS), an automatic nose-down trim function, had not been told it existed: the manufacturer, with the approval of the Federal Aviation Administration, removed it from the flight crew manual and training materials, and the Indonesian investigators found the missing guidance made it harder for crews to respond. That is not the whole record. The Lion Air crew the day before recovered without knowing of MCAS by cutting out the stabilizer trim, and the Ethiopian crew had received the bulletin and emergency directive issued after the first crash, which pointed to the cutout switches; the Ethiopian investigators say that guidance did not have its intended effect. Both investigations also list the single sensor, the repeated activations and the many alerts the crews faced at once. The record does not settle how much turned on disclosure: a federal court found in October 2022, in ruling that the families had rights as crime victims, that had Boeing not concealed MCAS from the Federal Aviation Administration's evaluators neither crash would have occurred, while the United States National Transportation Safety Board calls the Ethiopian finding on missing MCAS documentation misleading. The agent-world equivalent is an operator who has not been told what the agent is allowed to do
    After: Before the Lion Air crash, the pilots supervising the Maneuvering Characteristics Augmentation System (MCAS), an automatic nose-down trim function, had not been told it existed: the manufacturer, with the approval of the Federal Aviation Administration, removed it from the flight crew manual and training materials, and the Indonesian investigators found the missing guidance made it harder for crews to respond. That is not the whole record. The Lion Air crew the day before recovered without knowing of MCAS by cutting out the stabilizer trim, and the Ethiopian crew had received the bulletin and emergency directive issued after the first crash, which pointed to the cutout switches; the Ethiopian investigators say that guidance did not have its intended effect. Both investigations also list the single sensor, the repeated activations and the many alerts the crews faced at once. The record does not settle how much turned on disclosure: a federal court found in October 2022, in ruling that the families could assert rights as representatives of crime victims, that had Boeing not concealed MCAS's expansion to low speeds from the Federal Aviation Administration group that set pilot training requirements, neither crash would have occurred, while the United States National Transportation Safety Board calls the Ethiopian finding on missing MCAS documentation misleading. The agent-world equivalent is an operator who has not been told what the agent is allowed to do
  • 2026-10-21: Inference: value. Found in the editor's second, independent check of the interpretations, 21 october 2026: third check: abbreviation spelled out in the signed paragraph.
    Show the change
    Before: Before the Lion Air crash, the pilots supervising the Maneuvering Characteristics Augmentation System (MCAS), an automatic nose-down trim function, had not been told it existed: the manufacturer, with the approval of the Federal Aviation Administration, removed it from the flight crew manual and training materials, and the Indonesian investigators found the missing guidance made it harder for crews to respond. That is not the whole record. The Lion Air crew the day before recovered without knowing of MCAS by cutting out the stabilizer trim, and the Ethiopian crew had received the bulletin and emergency directive issued after the first crash, which pointed to the cutout switches; the Ethiopian investigators say that guidance did not have its intended effect. Both investigations also list the single sensor, the repeated activations and the many alerts the crews faced at once. The record does not settle how much turned on disclosure: a federal court found in October 2022, in ruling that the families had rights as crime victims, that had Boeing not concealed MCAS from the Federal Aviation Administration's evaluators neither crash would have occurred, while the US National Transportation Safety Board calls the Ethiopian finding on missing MCAS documentation misleading. The agent-world equivalent is an operator who has not been told what the agent is allowed to do
    After: Before the Lion Air crash, the pilots supervising the Maneuvering Characteristics Augmentation System (MCAS), an automatic nose-down trim function, had not been told it existed: the manufacturer, with the approval of the Federal Aviation Administration, removed it from the flight crew manual and training materials, and the Indonesian investigators found the missing guidance made it harder for crews to respond. That is not the whole record. The Lion Air crew the day before recovered without knowing of MCAS by cutting out the stabilizer trim, and the Ethiopian crew had received the bulletin and emergency directive issued after the first crash, which pointed to the cutout switches; the Ethiopian investigators say that guidance did not have its intended effect. Both investigations also list the single sensor, the repeated activations and the many alerts the crews faced at once. The record does not settle how much turned on disclosure: a federal court found in October 2022, in ruling that the families had rights as crime victims, that had Boeing not concealed MCAS from the Federal Aviation Administration's evaluators neither crash would have occurred, while the United States National Transportation Safety Board calls the Ethiopian finding on missing MCAS documentation misleading. The agent-world equivalent is an operator who has not been told what the agent is allowed to do
  • 2026-10-21: Inference: signed by. The interpretation's wording changed after the editor signed it (second, independent check of 21 october 2026); the signature is cleared so the editor signs the corrected wording.
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    Before: Saurabh Bhatnagar
    After:
  • 2026-10-21: Inference: value. Found in the editor's second, independent check of the interpretations, 21 october 2026: the paragraph gave only the side that discounts disclosure; the court's finding (ecf no. 116, 21 october 2022, pdf pages 11 and 14) points the other way, so both are stated.
    Show the change
    Before: Before the Lion Air crash, the pilots supervising the Maneuvering Characteristics Augmentation System (MCAS), an automatic nose-down trim function, had not been told it existed: the manufacturer, with the approval of the Federal Aviation Administration, removed it from the flight crew manual and training materials, and the Indonesian investigators found the missing guidance made it harder for crews to respond. That is not the whole record. The Lion Air crew the day before recovered without knowing of MCAS by cutting out the stabilizer trim, and the Ethiopian crew had received the bulletin and emergency directive issued after the first crash, which pointed to the cutout switches; the Ethiopian investigators say that guidance did not have its intended effect. Both investigations also list the single sensor, the repeated activations and the many alerts the crews faced at once. The record does not settle how much turned on disclosure: the US National Transportation Safety Board calls the Ethiopian finding on missing MCAS documentation misleading. The agent-world equivalent is an operator who has not been told what the agent is allowed to do
    After: Before the Lion Air crash, the pilots supervising the Maneuvering Characteristics Augmentation System (MCAS), an automatic nose-down trim function, had not been told it existed: the manufacturer, with the approval of the Federal Aviation Administration, removed it from the flight crew manual and training materials, and the Indonesian investigators found the missing guidance made it harder for crews to respond. That is not the whole record. The Lion Air crew the day before recovered without knowing of MCAS by cutting out the stabilizer trim, and the Ethiopian crew had received the bulletin and emergency directive issued after the first crash, which pointed to the cutout switches; the Ethiopian investigators say that guidance did not have its intended effect. Both investigations also list the single sensor, the repeated activations and the many alerts the crews faced at once. The record does not settle how much turned on disclosure: a federal court found in October 2022, in ruling that the families had rights as crime victims, that had Boeing not concealed MCAS from the Federal Aviation Administration's evaluators neither crash would have occurred, while the US National Transportation Safety Board calls the Ethiopian finding on missing MCAS documentation misleading. The agent-world equivalent is an operator who has not been told what the agent is allowed to do
  • 2026-10-21: Inference: value. Found in the editor's second, independent check of the interpretations, 21 october 2026: abbreviation spelled out at first use (house committee report).
    Show the change
    Before: Before the Lion Air crash, the pilots supervising MCAS, the automatic nose-down trim function, had not been told it existed: the manufacturer, with the approval of the Federal Aviation Administration, removed it from the flight crew manual and training materials, and the Indonesian investigators found the missing guidance made it harder for crews to respond. That is not the whole record. The Lion Air crew the day before recovered without knowing of MCAS by cutting out the stabilizer trim, and the Ethiopian crew had received the bulletin and emergency directive issued after the first crash, which pointed to the cutout switches; the Ethiopian investigators say that guidance did not have its intended effect. Both investigations also list the single sensor, the repeated activations and the many alerts the crews faced at once. The record does not settle how much turned on disclosure: the US National Transportation Safety Board calls the Ethiopian finding on missing MCAS documentation misleading. The agent-world equivalent is an operator who has not been told what the agent is allowed to do
    After: Before the Lion Air crash, the pilots supervising the Maneuvering Characteristics Augmentation System (MCAS), an automatic nose-down trim function, had not been told it existed: the manufacturer, with the approval of the Federal Aviation Administration, removed it from the flight crew manual and training materials, and the Indonesian investigators found the missing guidance made it harder for crews to respond. That is not the whole record. The Lion Air crew the day before recovered without knowing of MCAS by cutting out the stabilizer trim, and the Ethiopian crew had received the bulletin and emergency directive issued after the first crash, which pointed to the cutout switches; the Ethiopian investigators say that guidance did not have its intended effect. Both investigations also list the single sensor, the repeated activations and the many alerts the crews faced at once. The record does not settle how much turned on disclosure: the US National Transportation Safety Board calls the Ethiopian finding on missing MCAS documentation misleading. The agent-world equivalent is an operator who has not been told what the agent is allowed to do
  • 2026-10-21: Controls: c-r3. Editor's classification call of 21 october 2026 (call 4, accepted from pull request #74): on neither crash flight did the crew's takeover recover the aircraft; the day-before recovery on the lion air aircraft stays in the note.
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    Before: succeeded
    After: failed
  • 2026-10-20: Inference: value. Found in the editor's source re-check of 19-20 october 2026: the interpretation held for lion air 610 (house report; indonesian contributing factor 4: 'the absence of guidance on mcas ... made it more difficult for flight crews to properly respond') but overreached for the case as a whole. the indonesian report records the previous flight's crew recovering with the cutout switches; the ethiopian report says the post-crash bulletin and directive were distributed to all the operator's max pilots and 'did not have the intended effect' (contributing factor 2); and the national transportation safety board calls the documentation finding 'misleading'. the unchecked superlative ('the clearest case in the register') is removed. the interpretation was already unsigned; the editor must sign the new wording.
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    Before: {"value": "The clearest case in the Register of supervisors who could not do the job because no one told them what the system was permitted to do. The agent-world equivalent is an operator who does not know what the agent is allowed to do.", "source_ids": ["HOUSE"]}
    After: {"value": "Before the Lion Air crash, the pilots supervising MCAS, the automatic nose-down trim function, had not been told it existed: the manufacturer, with the approval of the Federal Aviation Administration, removed it from the flight crew manual and training materials, and the Indonesian investigators found the missing guidance made it harder for crews to respond. That is not the whole record. The Lion Air crew the day before recovered without knowing of MCAS by cutting out the stabilizer trim, and the Ethiopian crew had received the bulletin and emergency directive issued after the first crash, which pointed to the cutout switches; the Ethiopian investigators say that guidance did not have its intended effect. Both investigations also list the single sensor, the repeated activations and the many alerts the crews faced at once. The record does not settle how much turned on disclosure: the US National Transportation Safety Board calls the Ethiopian finding on missing MCAS documentation misleading. The agent-world equivalent is an operator who has not been told what the agent is allowed to do.", "source_ids": ["HOUSE", "KNKT", "ETH-AIB", "NTSB-ET302"]}
  • 2026-10-20: Controls: c-r3. Found in the editor's source re-check of 19-20 october 2026: the ethiopian report's history of flight (phases 4 and 5) records that the et302 crew also used the cutout switches, reported the trim 'not working', and restored the switches before the fourth mcas activation; the note now records both flights. bucket and confidence unchanged (the bucket is the editor's pending call).
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    Before: Crew recovery on the Lion Air flight the day before: after a jump-seat pilot noted the dive, the Captain cut out the stabilizer trim (one occurrence)
    After: Crew recovery on the Lion Air flight the day before: after a jump-seat pilot noted the dive, the Captain cut out the stabilizer trim (one occurrence). On Ethiopian 302 the crew also cut out the trim, could not trim manually, and returned the switches to normal about two and a half minutes later, before the fourth activation
  • 2026-10-20: Controls: c-x1. Found in the editor's source re-check of 19-20 october 2026: the ethiopian report says that if the elevated angle of attack persists for more than five seconds after a main electric trim input 'the mcas flight control law will command another stabilizer nose down trim input'; the indonesian report gives the 2.5 degree limit and says 'boeing also not considered repetitive erroneous mcas activations'. a magnitude limit existed; a limit on repetition did not. bucket and confidence unchanged.
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    Before: Activation limit per flight
    After: No limit on repeated activations: MCAS commanded another nose-down input whenever the high reading persisted five seconds after a pilot trim input; each input was limited to 2.5 degrees of stabilizer movement
  • 2026-10-20: Fields: recovery accountability. Found in the editor's source re-check of 19-20 october 2026: the 2024 breach finding was cited to the 2021 agreement, which cannot contain it, and the field stopped there. primary records now cited: the department's letter to the court of 14 may 2024 (ecf no. 199); the non-prosecution agreement of 29 may 2025 (paragraphs 3, 4 and 11); the court's order of 6 november 2025 (ecf no. 358), which also records the july 2024 plea agreement and its rejection on 5 december 2024; and the fifth circuit's revised opinion of 22 may 2026 denying the families' mandamus petitions.
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    Before: {"value": "Deferred prosecution agreement with the Department of Justice, January 2021, on a charge of conspiracy to defraud the United States over MCAS: $243.6 million criminal penalty, $1.77 billion to airline customers, and a $500 million fund for the families of those killed (about $2.5 billion in total). In 2024 the Department of Justice found Boeing had breached the agreement; later proceedings are not recorded here", "source_ids": ["DOJ-BA"]}
    After: {"value": "Deferred prosecution agreement with the Department of Justice, January 2021, on a charge of conspiracy to defraud the United States over MCAS: $243.6 million criminal penalty, $1.77 billion to airline customers, and a $500 million fund for the families of those killed (about $2.5 billion in total). On 14 May 2024 the Department told the court it had determined that Boeing breached the agreement by failing to design, implement and enforce a compliance and ethics program. On 5 December 2024 the court rejected a plea agreement the parties had submitted in July 2024. Under a non-prosecution agreement of 29 May 2025, Boeing admitted the facts amounted to conspiracy to defraud the United States by obstructing the FAA's Aircraft Evaluation Group, and agreed to pay a further $243.6 million penalty, $444.5 million for the victims' families and at least $455 million for compliance and safety programs. On 6 November 2025 the court dismissed the charge at the Department's request, while writing that the agreement 'fails to secure the necessary accountability to ensure the safety of the flying public'; the federal appeals court denied the families' petitions against the agreement and the dismissal (revised opinion, 22 May 2026). Civil suits by the families are not recorded here", "source_ids": ["DOJ-BA", "DOJ-BREACH", "DOJ-NPA", "DISMISSAL", "CA5-2026"]}
  • 2026-10-20: Fields: recovery technical. Found in the editor's source re-check of 19-20 october 2026: the field compressed two phases and left out the decisive step. the ethiopian report's history of flight (phases 3 to 5) records the cutout at about 05:40:38; that 'pitch increased when both pilots applied forces, pitch decreased when a single pilot applied force (force oscillated between 80 lbs and 110lbs)'; the switches 'restored to the normal position' by 05:43:11; a 4th mcas activation in which 'the stabilizer moved from 2.3 to 1 unit'; and 'despite calculated force of up to 180lbs, the pitch continued decreasing'. now attributed to the ethiopian report; type and confidence unchanged.
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    Before: The crews' attempts to counter the trim failed: on ET302 the first officer reported the manual trim was not working, and control-column forces of 80 to 110 lb did not stop the nose dropping
    After: The Ethiopian report records that on ET302 the crew cut out the stabilizer trim after the second MCAS activation; with electric trim off, the first officer said the trim was not working, tried it manually and said 'It is not working' at about 340 knots, and the two pilots held 80 to 110 lb on the control column, the nose rising only when both pulled. About two and a half minutes later the crew returned the cutout switches to normal; about five seconds after their next electric trim input a fourth activation moved the stabilizer from 2.3 to 1 unit, and the nose kept dropping despite up to 180 lb of column force
  • 2026-10-20: Fields: evidence causality. Found in the editor's source re-check of 19-20 october 2026: the national transportation safety board's release of 24 january 2023 says it 'agrees with the overall finding in the eaib report related to the role' of mcas, but that the report 'contains findings the ntsb said are unsupported by evidence', naming the electrical cause of the sensor failure (the board found 'impact with a foreign object, which was most likely a bird') and calling the documentation finding 'misleading'; it also refers to its 27 december 2022 comments on 'insufficient attention to the human performance aspects'. the ethiopian report (finding 65) attributes the malfunction to a 'production related intermittent electrical/electronic failure'. both accounts stated; marked disputed.
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    Before: {"value": "Both investigations identify MCAS activation on erroneous sensor data as central; the House report adds design, certification and disclosure failures", "source_ids": ["HOUSE", "KNKT", "ETH-AIB"], "disputed": false}
    After: {"value": "Both investigations identify MCAS activation on erroneous sensor data as central; the House report adds design, certification and disclosure failures. The US National Transportation Safety Board, which took part in the Ethiopian investigation, agrees on the role of MCAS but disputes parts of the Ethiopian report: it says the report gave crew performance insufficient attention; where the Ethiopian report attributes the sensor malfunction to a production-related electrical failure, the Board found the sensor vane was separated by a foreign object, most likely a bird; and it calls the finding on missing MCAS documentation for crews misleading, because Boeing had given the information to all 737 MAX operators four months before the crash", "source_ids": ["HOUSE", "KNKT", "ETH-AIB", "NTSB-ET302"], "disputed": true}
  • 2026-10-20: Fields: outcome. Found in the editor's source re-check of 19-20 october 2026: 'other regulators lifted their groundings later' had no linked source; the european union aviation safety agency's release of 27 january 2021 states the aircraft 'was grounded worldwide in march 2019' and approves its return to service in europe. 'as of 2022' disagreed with outcome.as_of; both now june 2026.
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    Before: {"value": "State: harm. 346 fatalities across two flights (189 on Lion Air 610, 157 on Ethiopian 302). Grounded in the United States from 13 March 2019 until the FAA rescinded its order on 18 November 2020, conditional on the required fixes; other regulators lifted their groundings later. As of 2022.", "source_ids": ["ETH-AIB", "KNKT", "FAA-RTS"]}
    After: {"value": "State: harm. 346 fatalities across two flights (189 on Lion Air 610, 157 on Ethiopian 302). Grounded worldwide from March 2019; in the United States from 13 March 2019 until the FAA rescinded its order on 18 November 2020, conditional on the required fixes; other regulators lifted their groundings later (the European Union Aviation Safety Agency on 27 January 2021). As of June 2026.", "source_ids": ["ETH-AIB", "KNKT", "FAA-RTS", "EASA-RTS"]}
  • 2026-10-20: Fields: envelope basis. Found in the editor's source re-check of 19-20 october 2026: an assertion must name who asserts it. the house report (p. 27-28) says that in a december 2018 briefing to the faa 'boeing also acknowledged that it did not reevaluate its single- and multiple-failure assessments of mcas after its engineers made design changes to the mcas software in 2016.' type and confidence unchanged.
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    Before: Boeing did not reevaluate its single- and multiple-failure assessments of MCAS after the 2016 design changes
    After: Boeing did not reevaluate its single- and multiple-failure assessments of MCAS after the 2016 design changes, as Boeing acknowledged in a December 2018 briefing to the FAA, according to the House committee report
  • 2026-10-20: Fields: envelope authority. Found in the editor's source re-check of 19-20 october 2026: the house report (p. 102) gives the figures: 'as originally designed, mcas was only capable of moving the horizontal stabilizer a maximum of 0.6 degrees' and, after the march 2016 redesign, 'a maximum of 2.5 degrees'. added for precision; the claim holds.
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    Before: Design authority was increased during development to a larger stabilizer movement than originally assessed; activation did not require both sensors to agree
    After: Design authority was increased during development to a larger stabilizer movement than originally assessed (from a maximum of 0.6 to 2.5 degrees of stabilizer movement, in March 2016); activation did not require both sensors to agree
  • 2026-10-20: Fields: mandate disclosed to supervisor. Found in the editor's source re-check of 19-20 october 2026: the field held for the period before the first crash but omitted two things the primary records show. the deferred prosecution agreement (paragraph 1(h), statement of facts paragraph 25) says 'two of the company's 737 max flight technical pilots deceived the faa aeg about mcas' while 'others in the company disclosed mcas's expanded operational scope' to the faa airworthiness staff. the house report and the ethiopian report record the 6-7 november 2018 bulletin and emergency directive, which did not mention mcas, and boeing's 10 november 2018 message describing mcas to operators, including ethiopian airlines.
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    Before: {"value": "Boeing, with FAA approval, removed references to MCAS from the flight crew operations manual and training materials; pilots were largely unaware of it", "source_ids": ["HOUSE"]}
    After: {"value": "Boeing, with FAA approval, removed references to MCAS from the flight crew operations manual and training materials; pilots were largely unaware of it. The deferred prosecution agreement records that two Boeing technical pilots deceived the FAA group that set pilot training requirements about MCAS, while others at Boeing disclosed its expanded scope to the FAA staff who assessed airworthiness. After the Lion Air crash, a Boeing bulletin (6 November 2018) and an FAA emergency airworthiness directive (7 November) warned of repeated nose-down trim from an erroneous angle-of-attack reading without naming MCAS, and on 10 November 2018 Boeing described MCAS in a message to airlines flying the MAX, including Ethiopian Airlines", "source_ids": ["HOUSE", "DOJ-BA", "ETH-AIB"]}
  • 2026-10-20: Fields: mandate objective: source ids. Found in the editor's source re-check of 19-20 october 2026: the indonesian report (section 2.5.1.1) states the purpose in one sentence: 'the mcas was needed in order to make the boeing 737-8 (max) handling characteristics so similar to the ng versions that no simulator training was needed for type rating.' added as a second source; the house wording holds.
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    Before: ["HOUSE"]
    After: ["HOUSE", "KNKT"]
  • 2026-10-20: Applicable rules. Found in the editor's source re-check of 19-20 october 2026: the deferred prosecution agreement was found breached in 2024 and replaced by the non-prosecution agreement of 29 may 2025, under which the charge was dismissed (ecf no. 358).
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    Before: ["FAA certification rules (Part 25)", "Deferred prosecution terms"]
    After: ["FAA certification rules (Part 25)", "Deferred prosecution agreement terms (2021), then non-prosecution agreement terms (2025)"]
  • 2026-10-20: Outcome: as of. Found in the editor's source re-check of 19-20 october 2026: the latest development found is the fifth circuit's revised opinion of 22 may 2026, with the mandate issued 18 june 2026 (department of justice case page); the outcome field said 'as of 2022' and the block said 2024, so both now read june 2026.
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    Before: 2024
    After: Jun 2026
  • 2026-10-20: Outcome: regime consequence. Found in the editor's source re-check of 19-20 october 2026: out of date. the department told the court on 14 may 2024 that boeing breached the agreement (ecf no. 199); the court dismissed the charge on 6 november 2025 after a non-prosecution agreement (ecf no. 358); the fifth circuit denied the families' mandamus petitions (revised opinion, 22 may 2026).
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    Before: deferred prosecution agreement; grounding
    After: deferred prosecution agreement (2021), found breached by the Department of Justice (2024); non-prosecution agreement and dismissal of the charge (2025); families' petitions against them denied on appeal (2026); grounding
  • 2026-10-20: Outcome: cost. Found in the editor's source re-check of 19-20 october 2026: the 2021 agreement's total is $2,513,600,000 (agreement, paragraph 7); the non-prosecution agreement of 29 may 2025 adds a remaining $243.6 million penalty, $444.5 million for victims' families and at least $455 million for compliance and safety programs (over $1.1 billion, per the government's status report of 23 may 2025). 'global grounding' had no linked source; the european union aviation safety agency states the aircraft 'was grounded worldwide in march 2019'. abbreviation spelled out.
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    Before: ~$2.5B DPA; global grounding
    After: about $2.5 billion under the 2021 deferred prosecution agreement and over $1.1 billion more under the 2025 non-prosecution agreement; worldwide grounding from March 2019
  • 2026-10-20: Context: mandate context text. Found in the editor's source re-check of 19-20 october 2026: true for the lion air crash (house report: pilots 'were precluded from knowing of the existence of mcas'), but the ethiopian report records that after the lion air accident 'the manufacturer revealed this feature of the pitch trim system as mcas, and provided description of it to operators, including ethiopian airlines'; the house report dates that message 10 november 2018.
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    Before: Production; mandate not disclosed to the supervising humans
    After: Production; MCAS was not disclosed to pilots before the first crash and was described to operators only after it
  • 2026-10-20: Context: autonomy level text. Found in the editor's source re-check of 19-20 october 2026: the ethiopian report (section 1.6.5) says the column cutout was inhibited while mcas was active, 'allowing airplane nose-down stabilizer motion with airplane nose-up column input', but that the pilots' electric trim switches override mcas and the stabilizer trim cutout switches remove its power; 'able to override the human' overstated it.
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    Before: Machine acts, human supervises, with the machine able to override the human
    After: Machine acts without pilot command, moving the stabilizer against the pilot's pull on the control column; the human supervises and can stop it with the trim switches or cut off its power
  • 2026-10-20: Title. Found in the editor's source re-check of 19-20 october 2026: 'with authority to override pilots' overstates the record. the house committee report describes mcas's 'potential effect on aircraft handling without pilot command', and the ethiopian report records repeated activations, but also that 'any main electric trim input would immediately override any mcas command' and that with a cutout switch at cutout 'neither main electric trim nor automatic trim can move the stabilizer'.
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    Before: Boeing 737 MAX MCAS: a flight-control function acts on a single sensor with authority to override pilots; Lion Air 610 (29 Oct 2018) and Ethiopian 302 (10 Mar 2019)
    After: Boeing 737 MAX MCAS: a flight-control function acts on a single sensor, repeatedly and without pilot command; Lion Air 610 (29 Oct 2018) and Ethiopian 302 (10 Mar 2019)
  • 2026-10-16: Outcome: as of. Found in an outside review of the published record on 16 october 2026: the record includes a 2024 finding, so the outcome is current as of 2024.
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    Before: 2022
    After: 2024
  • 2026-10-14: Controls. Editor decision 14 october 2026: new canonical control c-o2 (independent assurance before deployment) added for this gap.
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    Before: failed candidate 'Certification safety assessment'
    After: C-O2 (failed), medium confidence
  • 2026-10-14: Controls: c-r3. The indonesian report credits the captain with the recovery; aligns the control note with the corrected claim.
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    Before: Third pilot's intervention the day before Lion Air 610 (one occurrence)
    After: Crew recovery on the Lion Air flight the day before: after a jump-seat pilot noted the dive, the Captain cut out the stabilizer trim (one occurrence)
  • 2026-10-13: Fields. Independent check against the linked records before right-of-reply letters.
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    Before: third pilot credited with the recovery; 'pilots did not know it existed'; 'did not reevaluate MCAS'; grounding stated as global; objective 'handled like earlier 737s'
    After: Captain cut out the trim after the jump-seat pilot's observation; House report wording ('largely unaware', failure assessments not reevaluated); US grounding dates; objective as the House report frames it; 2024 breach finding noted
  • 2026-10-13: Fields and sources. Claims aligned to what each linked record says, found on review.
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    Before: House report typed as regulator; 'safety assessment did not reflect final design'; runaway-stabilizer sufficiency claim; grounding dates unsourced; 'later criminal proceedings'
    After: House majority-staff report typed as public record; reworded to 'did not reevaluate MCAS after the redesign'; recovery claim reworded to what the Ethiopian report records; grounding end cited to the FAA rescission; DOJ agreement terms from the agreement itself, later proceedings removed pending their own sources
  • 2026-10-13: Controls: c-i2. A control has one state per case; entries in two states merged into the state the record supports.
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    Before: failed: Single-sensor dependence; absent: Sensor disagreement check gating activation
    After: failed: Single-sensor dependence; Sensor disagreement check gating activation (absent)
  • 2026-10-06: Readout:accountability. Boeing is the manufacturer, not the operator; corrected in the 26-case readout.
    Show the change
    Before: accountability reached the operator
    After: accountability reached the maker of the automation (deferred prosecution agreement against Boeing)
Record history · 12 entries
  • 2026-10-28: No statement from Boeing within 14 days of the offer.
  • 2026-10-22: Follow-up note sent to Boeing on claims added in a correction round (the federal court's October 2022 finding that, had Boeing not concealed MCAS's expansion to low speeds from the FAA group setting pilot training, neither crash would have occurred (interpretation)); 14 days to reply on those points.
  • 2026-10-21: Source added: Second Memorandum Opinion and Order (Crime Victims' Rights Act), United States v. The Boeing Company, No. 4:21-cr-5-O (N.D. Tex.), 21 October 2022, ECF No. 116.
  • 2026-10-20: Source added: NTSB Publishes Additional Comments on Ethiopia's Final Report on 737 MAX 8 Accident.
  • 2026-10-20: Source added: EASA declares Boeing 737 MAX safe to return to service in Europe.
  • 2026-10-20: Source added: In re Naoise Connolly Ryan, et al., Nos. 25-11253 and 25-11254 (5th Cir.), revised opinion on petitions for rehearing, 22 May 2026.
  • 2026-10-20: Source added: Memorandum Opinion and Order granting the Government's motion to dismiss the Information, United States v. The Boeing Company, No. 4:21-cr-5-O (N.D. Tex.), ECF No. 358.
  • 2026-10-20: Source added: Non-Prosecution Agreement, United States v. The Boeing Company, No. 4:21-cr-00005-O (N.D. Tex.), 29 May 2025.
  • 2026-10-20: Source added: Department of Justice letter to Judge Reed O'Connor on Boeing's breach of the deferred prosecution agreement, United States v. The Boeing Company, No. 4:21-cr-00005-O (N.D. Tex.), ECF No. 199.
  • 2026-10-16: Interpretation reworded for readers before sign-off; its meaning is unchanged.
  • 2026-10-14: Right of reply offered to Boeing.
  • 2026-10-14: Checked by the editor against the linked records.

Controls that address what went wrong

6 controls missing or failed. The line under each is the concrete form it would have taken in this case.

Mandate disclosed to supervisor
Disclosure to operators
Failed · Mandate layer
Input redundancy and disagreement check
Failed: Single-sensor dependence. Absent: Sensor disagreement check gating activation.
Failed · Inputs layer
Authority limit on automation over humans
Authority limits
Failed · Envelope layer
Rate and magnitude limits
Absent: No limit on repeated activations: MCAS commanded another nose-down input whenever the high reading persisted five seconds after a pilot trim input. each input was limited to 2.5 degrees of stabilizer movement.
Absent · Action layer
Human takeover with a time window
Crew recovery on the Lion Air flight the day before: after a jump-seat pilot noted the dive, the Captain cut out the stabilizer trim (one occurrence). On Ethiopian 302 the crew also cut out the trim, could not trim manually, and returned the switches to normal about two and a half minutes later, before the fourth activation
Failed · Recovery layer
Independent assurance before deployment
Certification of MCAS (the House committee report identifies certification failures)
Failed · External layer

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How it unfolded, layer by layer

MandateWhat it was told to do
Who deployed it: Boeing, as designer; the operating airlines as principals in service. The task: Compensate for pitch-up handling at high angle of attack, consistent with the program's directive to avoid pilot simulator training requirements. Disclosed to supervisor: Boeing, with FAA approval, removed references to MCAS from the flight crew operations manual and training materials; pilots were largely unaware of it. The deferred prosecution agreement records that two Boeing technical pilots deceived the FAA group that set pilot training requirements about MCAS, while others at Boeing disclosed its expanded scope to the FAA staff who assessed airworthiness. After the Lion Air crash, a Boeing bulletin (6 November 2018) and an FAA emergency airworthiness directive (7 November) warned of repeated nose-down trim from an erroneous angle-of-attack reading without naming MCAS, and on 10 November 2018 Boeing described MCAS in a message to airlines flying the MAX, including Ethiopian Airlines.
ActorWhat acted
MCAS, acting through the horizontal stabilizer trim
InputsWhat it could see
A single angle-of-attack sensor; on both flights the sensor delivered erroneous data
DecisionHow it chose
Repeated activation, commanding nose-down trim each time the erroneous input persisted
EnvelopeWhat it was allowed to do
Authority it held: Design authority was increased during development to a larger stabilizer movement than originally assessed (from a maximum of 0.6 to 2.5 degrees of stabilizer movement, in March 2016); activation did not require both sensors to agree. Basis: Boeing did not reevaluate its single- and multiple-failure assessments of MCAS after the 2016 design changes, as Boeing acknowledged in a December 2018 briefing to the FAA, according to the House committee report.
ActionWhat it did
Repeated nose-down trim inputs the crews could not sustainably counter
OutcomeWhat happened
Ended in harm. Severity: fatalities.
EvidenceWhat can be proven
Pre-action warning: On the Lion Air flight the day before the crash the same behavior occurred; after an off-duty pilot in the jump seat noted the aircraft was diving, the Captain cut out the stabilizer trim and the crew continued on manual trim; the aircraft flew again. Causality: Both investigations identify MCAS activation on erroneous sensor data as central; the House report adds design, certification and disclosure failures. The US National Transportation Safety Board, which took part in the Ethiopian investigation, agrees on the role of MCAS but disputes parts of the Ethiopian report: it says the report gave crew performance insufficient attention; where the Ethiopian report attributes the sensor malfunction to a production-related electrical failure, the Board found the sensor vane was separated by a foreign object, most likely a bird; and it calls the finding on missing MCAS documentation for crews misleading, because Boeing had given the information to all 737 MAX operators four months before the crash.
RecoveryWhat could be stopped, undone, answered for
Automatic fallback: None; the system did not recognize its own input as erroneous. Technical recovery: The Ethiopian report records that on ET302 the crew cut out the stabilizer trim after the second MCAS activation; with electric trim off, the first officer said the trim was not working, tried it manually and said 'It is not working' at about 340 knots, and the two pilots held 80 to 110 lb on the control column, the nose rising only when both pulled. About two and a half minutes later the crew returned the cutout switches to normal; about five seconds after their next electric trim input a fourth activation moved the stabilizer from 2.3 to 1 unit, and the nose kept dropping despite up to 180 lb of column force. Accountability: Deferred prosecution agreement with the Department of Justice, January 2021, on a charge of conspiracy to defraud the United States over MCAS: $243.6 million criminal penalty, $1.77 billion to airline customers, and a $500 million fund for the families of those killed (about $2.5 billion in total). On 14 May 2024 the Department told the court it had determined that Boeing breached the agreement by failing to design, implement and enforce a compliance and ethics program. On 5 December 2024 the court rejected a plea agreement the parties had submitted in July 2024. Under a non-prosecution agreement of 29 May 2025, Boeing admitted the facts amounted to conspiracy to defraud the United States by obstructing the FAA's Aircraft Evaluation Group, and agreed to pay a further $243.6 million penalty, $444.5 million for the victims' families and at least $455 million for compliance and safety programs. On 6 November 2025 the court dismissed the charge at the Department's request, while writing that the agreement 'fails to secure the necessary accountability to ensure the safety of the flying public'; the federal appeals court denied the families' petitions against the agreement and the dismissal (revised opinion, 22 May 2026). Civil suits by the families are not recorded here.

The same gap in other cases

Cases where the same control was missing or failed. Those in another world are the cross-domain comparisons the Register exists to make.

ControlSame worldOther worlds
Rate and magnitude limits·Knight Capital 2012 (agents moving money), The DAO 2016 (agents moving money)
Human takeover with a time windowUber ATG, Tempe 2018·

Cost and accountability

Severityfatalities
Affected346 passengers and crew
Costabout $2.5 billion under the 2021 deferred prosecution agreement and over $1.1 billion more under the 2025 non-prosecution agreement; worldwide grounding from March 2019
Regulatory or legal consequencedeferred prosecution agreement (2021), found breached by the Department of Justice (2024); non-prosecution agreement and dismissal of the charge (2025); families' petitions against them denied on appeal (2026); grounding
Technical recoveryAutomatic fallback: None; the system did not recognize its own input as erroneous. Technical recovery: The Ethiopian report records that on ET302 the crew cut out the stabilizer trim after the second MCAS activation; with electric trim off, the first officer said the trim was not working, tried it manually and said 'It is not working' at about 340 knots, and the two pilots held 80 to 110 lb on the control column, the nose rising only when both pulled. About two and a half minutes later the crew returned the cutout switches to normal; about five seconds after their next electric trim input a fourth activation moved the stabilizer from 2.3 to 1 unit, and the nose kept dropping despite up to 180 lb of column force.
AccountabilityDeferred prosecution agreement with the Department of Justice, January 2021, on a charge of conspiracy to defraud the United States over MCAS: $243.6 million criminal penalty, $1.77 billion to airline customers, and a $500 million fund for the families of those killed (about $2.5 billion in total). On 14 May 2024 the Department told the court it had determined that Boeing breached the agreement by failing to design, implement and enforce a compliance and ethics program. On 5 December 2024 the court rejected a plea agreement the parties had submitted in July 2024. Under a non-prosecution agreement of 29 May 2025, Boeing admitted the facts amounted to conspiracy to defraud the United States by obstructing the FAA's Aircraft Evaluation Group, and agreed to pay a further $243.6 million penalty, $444.5 million for the victims' families and at least $455 million for compliance and safety programs. On 6 November 2025 the court dismissed the charge at the Department's request, while writing that the agreement 'fails to secure the necessary accountability to ensure the safety of the flying public'; the federal appeals court denied the families' petitions against the agreement and the dismissal (revised opinion, 22 May 2026). Civil suits by the families are not recorded here
InterpretationWhy it matters beyond its domain. Before the Lion Air crash, the pilots supervising the Maneuvering Characteristics Augmentation System (MCAS), an automatic nose-down trim function, had not been told it existed: the manufacturer, with the approval of the Federal Aviation Administration, removed it from the flight crew manual and training materials, and the Indonesian investigators found the missing guidance made it harder for crews to respond. That is not the whole record. The Lion Air crew the day before recovered without knowing of MCAS by cutting out the stabilizer trim, and the Ethiopian crew had received the bulletin and emergency directive issued after the first crash, which pointed to the cutout switches; the Ethiopian investigators say that guidance did not have its intended effect. Both investigations also list the single sensor, the repeated activations and the many alerts the crews faced at once. The record does not settle how much turned on disclosure: a federal court found in October 2022, in ruling that the families could assert rights as representatives of crime victims, that had Boeing not concealed MCAS's expansion to low speeds from the Federal Aviation Administration group that set pilot training requirements, neither crash would have occurred, while the United States National Transportation Safety Board calls the Ethiopian finding on missing MCAS documentation misleading. The agent-world equivalent is an operator who has not been told what the agent is allowed to do. Signed by Saurabh Bhatnagar on 2026-10-21.

Right of reply

Named partyStatus
BoeingOffered 2026-10-14; no statement as of 2026-10-28Respond for Boeing

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