Boeing 737 MAX groundings
|Cause||Airworthiness revoked after recurring flight control failure|
In March 2019, aviation authorities around the world grounded the Boeing 737 MAX passenger airliner after two new 737 MAX aircraft crashed within five months, killing all 346 people aboard the two flights Lion Air Flight 610 on October 29, 2018 and Ethiopian Airlines Flight 302 on March 10, 2019. After the first accident, Boeing instructed pilots to follow an existing procedure to counteract unexpected nosedives forced by the Maneuvering Characteristics Augmentation System (MCAS), a new automated flight control on the MAX that was omitted from crew manuals and training. The U.S. Federal Aviation Administration (FAA) issued an emergency airworthiness directive to mandate the Boeing information. In a private analysis, the FAA predicted further accidents if MCAS was not revised.
Ethiopian Airlines grounded its remaining MAX fleet on March 10, day of its crash. On March 11, the Civil Aviation Administration of China ordered the first nationwide grounding, followed by most other regulators in quick succession. The FAA resisted congressional pressure to ground the MAX and reaffirmed its airworthiness on March 11, but grounded the airplane on March 13 after receiving evidence of accident similarities. By March 18, all 387 airplanes, which served 8,600 flights each week for 59 airlines, were grounded worldwide. Boeing suspended deliveries to airlines, but produced another 400 aircraft before halting manufacturing in January 2020.
After the groundings, the U.S. Congress, FBI and ad hoc panels began investigating FAA certification of the MAX, particularly the delegation of authority that allowed Boeing to act on behalf of the FAA. Several system and manufacturing defects were uncovered, in addition to problems with MCAS. The company reversed its policy and recommended flight simulator training for all MAX pilots. The longest ever grounding for a U.S. airliner was estimated to cost Boeing $18.6 billion by March 2020.
Investigators published their findings on the first anniversaries of the accidents in October 2019 and March 2020. The Indonesian NTSC faulted airplane design, certification, maintenance, and flight crew actions. The Ethiopian ECAA, which determined that the flight crew had attempted the recovery procedure, assigned blame to the aircraft's software design. The U.S. NTSB concluded that malfunctions resulted in multiple cockpit alerts that likely confused the flight crews. The U.S. House of Representatives criticized Boeing's "culture of concealment" during certification and in the aftermath of both accidents.
- On October 29, 2018, a 737 MAX 8 operating Lion Air Flight 610 crashed after take-off from Jakarta, killing 189 people, leading Boeing to publicly unveil the MCAS, a new automated flight control on the MAX that could cause unintended nosedives, but was omitted from crew manuals and training.
- On November 6, 2018, Boeing issued a service bulletin warning that with "erroneous AOA data, the pitch trim system can trim the stabilizer nose down in increments lasting up to 10 seconds" which "can be stopped and reversed with the use of the electric stabilizer trim switches but may restart 5 seconds after" and instructed pilots to counteract it by running the Runaway stabilizer and manual trim procedure.
- On November 7, 2018, the FAA issued an Emergency airworthiness directive requiring revising "the AFM to provide the flight crew with runaway horizontal stabilizer trim procedures" when "repeated nose-down trim commands" are caused by "an erroneously high single AOA sensor".
- On December 3, 2018, the FAA conducted an unpublished "Transport Aircraft Risk Assessment Methodology” (TARAM) analysis that concluded, "if left uncorrected, the MCAS design flaw in the 737 Max could result in as many as 15 future fatal crashes over the life of the fleet”; it was exposed by the United States House Committee on Transportation and Infrastructure on December 11, 2019.
- On March 10, 2019, another 737 MAX 8 operating Ethiopian Airlines Flight 302 crashed shortly after take-off from Addis Ababa airport, killing all 157 on-board, due to a similar faulty MCAS, initiating a worldwide flight ban for the aircraft, starting with China.
- On March 13, 2019, the U.S. FAA was among the last to order the grounding of the 737 MAX, after claiming there was no reason: China had the most aircraft in service, 96, followed by the U.S. with 72, Canada with 39 and India with 21.
- On March 27, 2019, Boeing unveiled a software update to avoid MCAS errors, already developed and tested it in-flight, to be certified.
- On April 5, 2019, Boeing announced it was cutting 737 production by almost a fifth, to 42 aircraft monthly, anticipating a prolonged grounding, and had formed an internal design review committee.
- On June 18, 2019, IAG committed to the 737 MAX with a letter of intent for 200 at the Paris air show, followed by Turkish SunExpress and Air Astana later in the year.
- On June 26, 2019, flight tests for the FAA uncovered a data processing issue affecting the pilots' ability to perform the "runaway stabiliser" procedure to respond to MCAS errors.
- On October 30, 2019, Boeing CEO Dennis Muilenburg testified before U.S. Congress committees, defending Boeing's safety culture and denying knowledge of internal messages in which Boeing's former chief technical pilot said he had unknowingly lied to regulators, and voiced its concerns on MCAS.
- In November 2019, the FAA revoked Boeing's authority to issue airworthiness certificates for individual MAX airplanes.
- On November 22, 2019, Boeing unveiled the first 737 MAX 10 flight-test aircraft.
- On December 17, 2019, Boeing confirmed the suspension of 737 MAX production from January 2020.
- On December 23, 2019, Dennis Muilenburg resigned, to be replaced by board chairman David Calhoun.
- On January 7, 2020, Boeing recommended "simulator training in addition to computer based training".
- On January 9, 2020, Boeing released previous messages in which it claimed no flight simulator time was needed for pilots, and distanced itself from emails mocking airlines and the FAA, and criticising the Max design.
- On January 13, 2020, David Calhoun became CEO, pledging to improve Boeing’s commitment to safety and transparency, and estimating the return to service in mid-2020.
- On January 21, 2020, Boeing estimated the ungrounding could begin in mid-2020.
After the Ethiopian Airlines crash, China and most other aviation authorities preceded the U.S. Federal Aviation Administration (FAA), the certifying agency for the MAX, in grounding the airliner over perceived safety risks. The FAA issued a Continued Airworthiness Notification to the International Community on March 11 and resisted pressure from U.S. lawmakers to ground the aircraft. Boeing CEO Dennis Muilenburg called U.S. president Trump on March 12 to assure him the airplane was safe. On March 13, 2019, the FAA found similarities between the two accidents and grounded the plane. About 30 MAX aircraft were flying in U.S. airspace at the time and were allowed to reach their destinations. By March 18, regulators grounded all 387 MAX aircraft in service with 59 airlines worldwide and making 8,600 flights each week. Several ferry flights were operated with flaps extended to circumvent MCAS activation.
The grounding subsequently became the longest ever of a U.S. airliner. As of January 2020, another 400 newly-manufactured aircraft await delivery to airlines pending the aircraft's return to service.
Lion Air Flight 610
Preliminary investigations revealed serious flight control problems that traumatized passengers and crew on the aircraft's previous flight, as well as signs of angle-of-attack (AoA) sensor and other instrument failures on that and previous flights, tied to a design flaw involving the Maneuvering Characteristics Augmentation System (MCAS) of the 737 MAX series. The report tentatively attributed the accident to the erroneous angle-of-attack (AoA) data and automatic nose-down trim commanded by MCAS. The defective angle-of-attack vane was a "dubious" used part that had been replaced on the captain's side, according to the aircraft's maintenance records.
The NTSC final report, published on October 23, 2019 was prepared with assistance from the U.S. NTSB. NTSC's investigator Nurcahyo Utomo identified nine factors to the accident, saying:
"The nine factors are the root problem; they cannot be separated. Not one is contributing more than the other. Unlike NTSB reports that identify the primary cause of accidents and then list contributing issues determined to be less significant, Indonesia is following a convention used by many foreign regulators of listing causal factors without ranking them".
Ethiopian Airlines Flight 302
The initial reports for Flight 302 found that the pilots struggled to control the airplane in a manner similar to the Lion Air flight 610 crash. On March 13, 2019, the FAA announced that evidence from the crash site and satellite data on Flight 302 suggested that it might have suffered from the same problem as Lion Air Flight 610 in that the jackscrew controlling the pitch of the horizontal stabilizer of the crashed Flight 302, was found to be set in the full "nose down" position, similar to Lion Air Flight 610. This further implicated MCAS as contributory to the crash.
Ethiopian Airlines spokesman Biniyam Demssie said that the procedures for disabling MCAS had just been incorporated into pilot training. "All the pilots flying the MAX received the training after the Indonesia crash," he said. "There was a directive by Boeing, so they took that training." Despite following the procedure, the pilots could not recover.
The Ethiopian Civil Aviation Authority (ECAA) is leading investigations for Flight 302. The United States Federal Aviation Administration will also assist in the investigation. Both the cockpit voice recorder and the flight data recorder were recovered from the crash site on March 11, 2019. The French aviation accident investigation agency BEA announced that it would analyze the flight recorders from the flight. BEA received the flight recorders on March 14, 2019.
On March 17, 2019, the Ethiopia's transport minister Dagmawit Moges announced that "the black box has been found in a good condition that enabled us to extract almost all the data inside" and that the preliminary data retrieved from the flight data recorder show a "clear similarity" with those of Lion Air Flight 610 which crashed off Indonesia. Due to this finding, some experts in Indonesia suggested that the NTSC should cooperate with Flight 302's investigation team. Later on the evening, the NTSC offered assistance to Flight 302's investigation team, stating that the committee and the Indonesian Transportation Ministry would send investigators and representatives from the government to assist with the investigation of the crash.
The Ethiopian Civil Aviation Authority published an interim report on March 9, 2020, one day before the March 10 anniversary of the crash. Investigators have tentatively concluded that the crash was caused by the aircraft's design.
On November 6, 2018, four days before it identified MCAS by name, Boeing published a supplementary service bulletin prompted by the first crash. The bulletin describes warnings triggered by erroneous AoA data, and referred pilots to a "non-normal runaway trim" procedure as resolution, specifying a narrow window of a few seconds before the system would reactivate and pitch the nose down again. The FAA issued an emergency airworthiness directive, 2018-23-51, on November 7, 2018 requiring the bulletin's inclusion in the flight manuals, and that pilots immediately review the new information provided. On March 11, FAA defended the aircraft against groundings citing these emergency procedures (Continued Airworthiness Notification to the International Community) for operators.
In December 2018, a month after the Lion Air accident, the FAA had conducted an internal safety risk analysis predicted fifteen more crashes with no repairs to MCAS, but that report was not revealed until the U.S. House hearing in December 2019. FAA's administrator, Stephen Dickson, who assumed the position during the accident investigations, said in retrospect that the accident risk was unsatisfactory.
On September 26, 2019, the NTSB released the results of its review of potential lapses in the design and approval of the 737 MAX.(p1) The NTSB report concludes that assumptions "that Boeing used in its functional hazard assessment of uncommanded MCAS function for the 737 MAX did not adequately consider and account for the impact that multiple flight deck alerts and indications could have on pilots' responses to the hazard". When Boeing induced a stabilizer trim input that simulated the stabilizer moving consistent with the MCAS function, "... the specific failure modes that could lead to unintended MCAS activation (such as an erroneous high AOA input to the MCAS) were not simulated as part of these functional hazard assessment validation tests. As a result, additional flight deck effects (such as IAS DISAGREE and ALT DISAGREE alerts and stick shaker activation) resulting from the same underlying failure (for example, erroneous AOA) were not simulated and were not in the stabilizer trim safety assessment report reviewed by the NTSB."
The NTSB questioned the long-held industry and FAA practice of assuming the nearly instantaneous responses of highly trained test pilots as opposed to pilots of all levels of experience to verify human factors in aircraft safety. The NTSB expressed concerns that the process used to evaluate the original design needs improvement because that process is still in use to certify current and future aircraft and system designs. The FAA could for example randomly sample pools from the worldwide pilot community to get a more representative assessment of cockpit situations.
- Indonesia, for Lion Air Flight 610 as state of registration, state of occurrence and state of operator.
- Ethiopia, for Ethiopian Airlines Flight 302, as state of registration, state of occurrence and state of operator.
- The United States, as state of manufacturer and issuer of the type certificate.
The participating state or national transportation safety bureaus are the NTSB for the US and the NTSC for Indonesia. Australia and Singapore also offered technical assistance, shortly after the Lion Air accident, regarding data recovery from the new generation flight recorders (FDR). With the exception of Ethiopia, the officially recognised countries are members of the Joint Authorities Technical Review (JATR).
Type certification and return to service
On March 11, 2019, a U.S. federal grand jury issued a subpoena on behalf of the U.S. Justice Department (DOJ) for documents related to development of the 737 MAX. On March 19, 2019, the U.S. Department of Transportation requested the Office of Inspector General to conduct an audit on the 737 MAX certification process. Under a system known as the Organization Designation Authorization, the FAA allowed manufacturers like Boeing to act on its behalf, while the agency retains legal authority to issue a type certificate. The goal for Boeing was to ensure the aircraft retains a compatible type rating with all other aircraft in the 737 family, thus avoiding costly simulator training and the need to learn of new systems like the MCAS.
Over the next several months, The Seattle Times's coverage of the ongoing crisis revealed how management decisions at Boeing and the FAA pushed for cost-saving solutions, but ultimately produced a flawed design with insufficient oversight. 
In November 2019, the FAA suspended Boeing's authority to issue individual airworthiness certificates for MAX aircraft. In February 2020, the DOJ was conducting an ongoing investigation into whether Boeing lied to the FAA. In March 2020, the House of Representatives criticized Boeing's culture of concealment and its undue influence over the FAA, as exemplified during certification and in the aftermath of the crashes.
By convention, aviation regulators worldwide accept the certification of aircraft from the country of manufacture and do not review those certifications in much detail. However, since the fatal accidents and grounding of 737 MAX several aviation authorities, particularly the European EASA, will conduct their assessments and validation tests of the MAX prior to authorizing it in their controlled airspace. As of October 2019 the disagreements over various system revision details, Level of Involvement (LoI) between the two leading aviation authorities, FAA and EASA, as well as Boeing's new recommendation of simulator training could delay the 737 MAX return to service.
Maneuvering Characteristics Augmentation System
The Maneuvering Characteristics Augmentation System (MCAS) is a flight control law (software) embedded into the Boeing 737 MAX flight control system which attempts to mimic pitching behavior similar to aircraft in the previous generation of the series, the Boeing 737 NG. When MCAS detects that the aircraft is operating in manual flight, with flaps up, at an elevated angle of attack (AoA), it adjusts the horizontal stabilizer trim to add positive force feedback (a "nose heavy" feel), through the control column, so the pilot will not inadvertently pull the airplane up too steeply, potentially causing a stall. Contrary to descriptions in news reports, however, Boeing claims that MCAS is not an anti-stall system. Stabilizer movement commanded by MCAS pushes down the nose of the airplane automatically without pilot input.
MCAS on the MAX was designed to activate using input from only one of the airplane's two angle of attack sensors, making the system susceptible to a single point of failure. Boeing omitted a description of MCAS from MAX flight manuals, leaving pilots unaware of the system when the airplane entered service. In April 2019, Boeing admitted that MCAS played a role in the fatal crashes of Lion Air Flight 610 and Ethiopian Airlines Flight 302. The first time Boeing publicly revealed the existence of MCAS on the 737 MAX was in a message to airline operators and other aviation interests on November 10, 2018, twelve days after the Lion Air crash. Boeing had also been aware of other software issues that suppressed a crucial AoA disagree message. With no knowledge of MCAS and its behavior, the pilots of the Lion Air flight, the first to crash, were at a disadvantage when attempting to respond to the system's erroneous activation. Procedures emphasized by Boeing and the FAA did not prevent the later Ethiopian Airlines crash, which led to the worldwide grounding of the airliner.
MCAS was first deployed on the Boeing KC-46 Air Force tanker, where it "similarly moves the stabilizer in a wind-up turn". Unlike the 737 MAX, however, MCAS could be overridden on the KC-46 by pulling back on its control column. The Wall Street Journal reported in May 2019 that Boeing failed to share information about that issue for "about a year" before the Lion Air crash in Indonesia.
After the Boeing 737 MAX groundings, reactions came from multiple organizations. Boeing initially expressed its sympathy to the relatives of the Lion Air Flight 610 and Ethiopian Airlines Flight 302 crashes victims, but defended the aircraft against any faults until disproven by evidence. Boeing provided several outdated return to service timelines, the soonest of which was "in the coming weeks" following the grounding. Public observers commented upon the "cozy relationship" that exists between the industry and its regulators.
After Boeing's crisis management failed to appease stakeholder concerns with the aircraft, the board removed Dennis Muilenburg as chairman and replaced him with David L. Calhoun on October 11, 2019. Airbus, its main competitor, is unwilling to put the blame on Boeing's engineering as the certification process could be more difficult for every airframer, and its production capacities are already maximized.
Pilots and flight attendants opinions are mixed as some expressed confidence in the certification renewal, while others are disappointed as Boeing had hidden an important safety feature to their knowledge. Most airlines seek compensation from Boeing to cover costs of the disruption, while the 737 MAX received some support when International Airlines Group (IAG) announced at the June 2019 Paris Air Show it could order 200 jets. Opinion polls suggested most passengers are reluctant to fly again aboard the 737 MAX when it will be reintroduced, while most should be comfortable boarding it again after some time passes to prove its safe operations.
Financial and economic effects
The Boeing 737 MAX groundings have had a deep financial effect on the aviation industry and a significant effect on the national economy of the United States. No airline took delivery of the MAX during grounding. Boeing slowed MAX production to 42 aircraft per month until in January 2020, when they halted until the airplane is reapproved by regulators. Boeing has suffered directly through increased costs, loss of sales and revenue, loss of reputation, victims litigation, client compensation, decreased credit rating and lowered stock value. In January 2020, the company estimated a loss of $18.4 billion for 2019, and it reported 183 canceled MAX orders for the year.
In February 2020, the global coronavirus pandemic and the resulting travel bans created further uncertainty and complications for Boeing. In March 2020, news that Boeing was seeking a $60 billion bailout caused a steep drop in its stock price. Its extensive supply chain providing aircraft components and flight simulators suffered similar losses, as did the aircraft services industry, including crew training, the aftermarket and the aviation insurance industry. Its customers, the airlines and aircraft lessors, had their operations and strategic plans severely disrupted.[not verified in body]
- Qantas Flight 72: data failure causing pitch down, severely injuring passengers
- Air France Flight 447: fatal accident following data and pitot tube failure and autopilot disablement
- Turkish Airlines Flight 1951: Dutch authorities have reopened the accident probe into this 2009 accident involving the prior generation 737-800 series aircraft.
- Graham Dunn (March 13, 2020). "Timeline of the twists and turns in the grounding of the Boeing 737 Max". Flightglobal.
- Jon Ostrower (November 7, 2018). "Boeing nearing 737 Max fleet bulletin on AoA warning after Lion Air crash". The Air Current.
- "Emergency Airworthiness Directive (AD) 2018-23-51" (PDF). FAA. November 7, 2018.
- Jon Hemmerdinger, Boston (December 12, 2019). "FAA 2018 analysis warned of 15 fatal Max crashes months before second accident". Flightglobal.
- "Boeing Statement on 737 MAX Simulator Training" (Press release). Boeing. January 7, 2020.
- Frost, Natasha. "The US is increasingly alone in not grounding the Boeing 737 Max". Quartz. Retrieved February 24, 2020.
- "U.S. Senate to hold crash hearing as lawmakers urge grounding Boeing 737 MAX 8". Reuters. March 12, 2019.
- Zeleny, Jeff; Schouten, Fredreka (March 12, 2019). "Trump speaks to Boeing CEO following tweets on airline technology". CNN. Retrieved December 19, 2019.
- Kaplan, Thomas; Austen, Ian; Gebrekidan, Selam (March 13, 2019). "U.S. Grounds Boeing Planes, After Days of Pressure". The New York Times. Retrieved March 14, 2019.
- "Boeing 737 Max 8 planes grounded after Ethiopian crash". CNN. March 13, 2019. Retrieved March 15, 2019.
- Lu, Denise; Mccann, Allison; Wu, Jin; Lai, K.K. Rebecca (March 13, 2019). "From 8,600 Flights to Zero: Grounding the Boeing 737 Max 8". The New York Times. Retrieved December 24, 2019.
- Campbell, Darryl (October 23, 2019). "The 737 built Southwest, and the 737 Max could be its undoing". The Verge. Retrieved February 27, 2020.
- "Boeing Statement on Lion Air Flight 610 Preliminary Report" (Press release). Boeing. November 27, 2018.
- Picheta, Rob (March 10, 2019). "Ethiopian Airlines crash is the second disaster involving Boeing 737 MAX 8 in months". CNN. Retrieved March 10, 2019.
- Langewiesche, William (September 18, 2019). "What Really Brought Down the Boeing 737 Max?". The New York Times Magazine.
- "Indonesia to Fault 737 MAX Design, U.S. Oversight in Lion Air Crash Report". msn.com. Retrieved October 28, 2019.
- Pasztor, Andy; Tangel, Andrew (September 22, 2019). "Indonesia to Fault 737 MAX Design, U.S. Oversight in Lion Air Crash Report". The Wall Street Journal. Retrieved September 23, 2019.
- Liebermann, Oren. "Investigators spread blame in Lion Air crash, but mostly fault Boeing and FAA". CNN. Retrieved October 26, 2019.
- Pasztor, Andy; Otto, Ben; Tangel, Andrew (October 25, 2019). "Boeing, FAA and Lion Air Failures Laid Bare in 737 MAX Crash Report". The Wall Street Journal. Retrieved October 25, 2019.
- "Boeing expects 737 Max to fly again by New Year". BBC News Online. October 23, 2019. Retrieved October 23, 2019.
- "Boeing fires commercial planes boss as 737 MAX crisis deepens: SKY". sky. October 23, 2019. Retrieved October 23, 2019.
- Aircraft Accident Investigation Report - Update. Final Report (Aviation Division): PT. Lion Mentari Airlines; Boeing 737-8 (MAX); PK-LQP, Tanjung Karawang, West Java, 29 October 2018 (PDF). October 25, 2019.
- "U.S. Joins Other Nations in Grounding Boeing Plane". The New York Times. March 13, 2019. Retrieved March 15, 2019.
- "Piece Found at Boeing 737 Crash Site Shows Jet Was Set to Dive". Bloomberg News. March 14, 2019. Retrieved March 16, 2019.
- Nicas, Jack; Kaplan, Thomas; Glanz, James (March 15, 2019). "New Evidence in Ethiopian 737 Crash Points to Connection to Earlier Disaster". The New York Times. Retrieved March 15, 2019.
- Glanz, James; Lai, K.K. Rebecca; Wu, Jin (March 13, 2019). "Why Investigators Fear the Two Boeing 737s Crashed for Similar Reasons". The New York Times. Retrieved March 15, 2019.
- Lazo, Luz; Schemm, Paul, Aratani, Lori. "Investigators find 2nd piece of key evidence in crash of Boeing 737 Max 8 in Ethiopia". The Washington Post. Archived from the original on 17 March 2019. Retrieved 16 March 2019.CS1 maint: multiple names: authors list (link)
- Schemm, Paul (March 13, 2019). "Ethiopian pilots received new training for 737 Max after Indonesian crash". The Washington Post.
- Gates, Dominic (April 3, 2019). "Why Boeing's emergency directions may have failed to save 737 MAX". The Seattle Times. Retrieved September 27, 2019.
- Siddiqui, Faiz (10 March 2019). "U. S. authorities to assist in investigation of Ethiopian Airlines crash that killed 157". The Washington Post. Archived from the original on 11 March 2019. Retrieved 10 March 2019.
- McKirdy, Euan; Berlinger, Joshua; Levenson, Eric. "Ethiopian Airlines plane crash". CNN. Archived from the original on 11 March 2019. Retrieved 11 March 2019.
- Hepher, Tim (13 March 2019). "France to analyze Ethiopian Airlines flight recorders: spokesman". Reuters. Archived from the original on 14 March 2019. Retrieved 14 March 2019.
- Kiernan, Kristy. "The Black Boxes From Ethiopian Flight 302: What's On Them And What Investigators Will Look For". Forbes. Archived from the original on 15 March 2019. Retrieved 16 March 2019.
- "Data on Ethiopia crash: 'Clear similarity' to Indonesia crash". Politico. Archived from the original on 27 March 2019. Retrieved 25 March 2019.
- Schemm, Paul (March 17, 2019). "'Black box' data show 'clear similarities' between Boeing jet crashes, official says". Los Angeles Times. The Washington Post. Retrieved March 22, 2019.
- Schemm, Paul (March 17, 2019). "Ethiopian official: Black box data shows 'clear similarities' between Ethiopian Airlines, Lion Air crashes". The Washington Post. Retrieved July 28, 2019.
- Mohammad Azka, Rinaldi. "Alasan KNKT Minta Dilibatkan Menginvestigasi Tragedi Ethiopian Airlines" [Reasons NTSC Asked To Be Involved In Investigating Ethiopian Airlines Tragedy] (in Indonesian). Bisnis. Archived from the original on 15 March 2019. Retrieved 14 March 2019.
- Christy Rosana, Fransisca. "KNKT Tawarkan Bantuan Investigasi Kecelakaan Ethiopian Airlines" [NTSC Offers Ethiopian Airlines Accident Investigation Assistance] (in Indonesian). Tempo. Archived from the original on 15 March 2019. Retrieved 14 March 2019.
- "Aircraft Accident Investigation Bureau Interim Report" (PDF). Ethiopian Civil Aviation Authority, Ministry of Transport (Ethiopia). March 9, 2020. Retrieved March 25, 2020.
- Levin, Alan (March 7, 2020). "Boeing Set to Get Blame in Ethiopian Report on Crash of 737 Max". Bloomberg. Retrieved March 7, 2020.
- Marks, Simon; Dahir, Abdi Latif (March 9, 2020). "Ethiopian Report on 737 Max Crash Blames Boeing". The New York Times. ISSN 0362-4331. Retrieved March 11, 2020.
- "Boeing nearing 737 Max fleet bulletin on AoA warning after Lion Air crash". The Air Current. November 7, 2018. Retrieved July 10, 2019.
- "FAA issues emergency AD regarding potential erroneous AOA input on Boeing 737 MAX". ASN News. November 7, 2018. Retrieved June 7, 2019.
- Tangel, Andrew; Pasztor, Andy (July 31, 2019). "Regulators Found High Risk of Emergency After First Boeing MAX Crash". The Wall Street Journal..
- Kitroeff, Natalie (September 26, 2019). "Boeing Underestimated Cockpit Chaos on 737 Max, N.T.S.B. Says". The New York Times. ISSN 0362-4331. Retrieved September 26, 2019.
- "Safety Recommendation Report: Assumptions Used in the Safety Assessment Process and the Effects of Multiple Alerts and Indications on Pilot Performance" (PDF). NTSB. September 19, 2019. Retrieved September 26, 2019. Lay summary. This article incorporates public domain material from websites or documents of the National Transportation Safety Board.
- "NTSB Issues 7 Safety Recommendations to FAA related to Ongoing Lion Air, Ethiopian Airlines Crash Investigations". NTSB. Retrieved September 30, 2019.
- Hill, Andrew (October 6, 2019). "Boeing report highlights human factors no company should ignore". Financial Times.
- Pasztor, Andy (September 26, 2019). "Plane Tests Must Use Average Pilots, NTSB Says After 737 MAX Crashes". The Wall Street Journal. Retrieved September 27, 2019.
- "Boeing Failed to Predict That Slew of 737 Max Warning Alarms Would Confuse Pilots, Investigators Say". Time. Retrieved September 27, 2019.
- ICAO fact sheet: Accident investigation (PDF). ICAO. 2016.
- Hall, James E. (March 13, 2019). "The 737 Max Is Grounded, No Thanks to the F.A.A." The New York Times. ISSN 0362-4331. Retrieved July 5, 2019.
- Tangel, Andrew; Pasztor, Andy; Wall, Robert (March 18, 2019). "Prosecutors, Transportation Department Scrutinize Development of Boeing's 737 MAX". The Wall Street Journal. Retrieved March 17, 2019.
- Woodyard, Chris (March 18, 2019). "Ethiopian Airlines crash raises questions about Boeing 737 Max certification process". USA Today.
- Levin, Alan; Robison, Peter (March 18, 2019). "Boeing Plane Certification Probe Began Before Second Crash". Bloomberg News.
- The Secretary of Transportation. "Audit of Certification for the Boeing 737 MAX 8" (PDF). Memorandum from the Secretary. U.S. Department of Transportation.
- staff, Seattle Times (December 15, 2019). "Boeing's 737 MAX Crisis: Coverage by The Seattle Times". The Seattle Times. Retrieved March 5, 2020.
- Slotnick, David. "The DOJ is reportedly probing whether Boeing's chief pilot misled regulators over the 737 Max". Business Insider. Retrieved February 22, 2020.
- "Europe and Canada Just Signaled They Don't Trust the FAA's Investigation of the Boeing 737 MAX". Time. Retrieved March 20, 2019.
- Pasztor, Andy; Tangel, Andrew (October 8, 2019). "Friction Between U.S., European Regulators Could Delay 737 MAX Return to Service". The Wall Street Journal. Retrieved October 8, 2019.
- Laris, Michael (June 19, 2019). "Changes to flawed Boeing 737 Max were kept from pilots, DeFazio says". The Washington Post. Retrieved February 29, 2020.
- Hradecky, Simon (January 14, 2019). "Crash: Lion B38M near Jakarta on Oct 29th 2018, aircraft lost height and crashed into Java Sea, wrong AoA data". The Aviation Herald. Retrieved March 2, 2020.
- "The inside story of MCAS: How Boeing's 737 MAX system gained power and lost safeguards". The Seattle Times. June 22, 2019. Retrieved June 24, 2019.
- Andy Pasztor; Andrew Tangel; Alison Sider (May 6, 2019). "Boeing Knew of Problem for a Year". Wall Street Journal. p. A1.
- "Boeing refuses to play ball as Dutch MPs reopen 2009 crash involving 737". smmry.com. Retrieved February 8, 2020.
- The real reason Boeing's new plane crashed twice. Vox Videos. April 15, 2019.
- Travis, Gregory (April 18, 2019). "How the Boeing 737 Max Disaster Looks to a Software Developer". IEEE Spectrum.
- "Timeline: The Boeing 737 MAX Crisis". Aviation Week Network. May 16, 2019.
- Leggett, Theo (May 17, 2019). "What went wrong inside Boeing's cockpit?". BBC News Online.
- Cox, John (May 20, 2019). "This [the emergency the pilots faced] is not simple". Leeham News.
- Gelles, David; Wichter, Zach (July 18, 2019). "Boeing 737 Max: The Latest on the Deadly Crashes and the Fallout". The New York Times.
- Broderick, Sean (August 15, 2019). "The MAX Saga, One Question At A Time". Aviation Week & Space Technology.
- Hemmerdinger, Jon (September 13, 2019). "Six months on from the Boeing 737 Max grounding". FlightGlobal.
- "Boeing 737 MAX Flight Control System - Observations, Findings, and Recommendations" (PDF). Joint Authorities Technical Review. October 11, 2019.
- "System Failure: The Boeing Crashes". Al Jazeera Media Network. October 16, 2019.
- David Kaminski-Morrow (March 13, 2020). "Why restarting Max production is just the start of Boeing's delivery challenges". FlightGlobal.
- Jon Hemmerdinger (March 13, 2020). "How the 737 Max grounding changed commercial aerospace". FlightGlobal.
- Dan Thisdell (March 13, 2020). "Tarnished Max brand presents major challenge for Boeing". FlightGlobal.