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March 13, 2019 (U.S. grounding)Peer-reviewed · 2 sourcesWell documented

Two Crashes Ground the Boeing 737 MAX Worldwide

A single faulty sensor and a hidden flight-control system bring down two airliners and 346 people

On the timeline · around March 13, 2019 (U.S. grounding) · Modern AviationModern AviationTwo Crashes Ground the Boeing 737 MAX Worldwide19901995200020052010201520202025

Quick facts

Lion Air Flight 610
October 29, 2018, 189 killed
Ethiopian Airlines Flight 302
March 10, 2019, 157 killed
U.S. grounding
March 13, 2019 - November 18, 2020 (21 months)
Faulty system
MCAS, relying on single angle-of-attack sensor

What happened

Boeing's 737 MAX 8 was involved in two crashes within five months: Lion Air Flight 610 crashed into the Java Sea on October 29, 2018, killing all 189 aboard, and Ethiopian Airlines Flight 302 crashed shortly after takeoff on March 10, 2019, killing all 157 aboard, a combined 346 deaths. Both crashes were traced to the Maneuvering Characteristics Augmentation System, software designed to push the aircraft's nose down automatically to prevent an aerodynamic stall, which relied on a single angle-of-attack sensor with no backup; in the Lion Air crash, MCAS forced the aircraft's nose down 26 times in the plane's final 10 minutes. Most airlines and regulators worldwide had already grounded the aircraft when the United States, through the FAA, grounded all 387 in-service 737 MAX jets on March 13, 2019. The fleet remained grounded for 21 months before the FAA rescinded the order on November 18, 2020.

Why it matters

The 737 MAX crashes exposed that pilots had not been told MCAS existed and had received no simulator training on it before the Lion Air crash, and the FAA's own certification process was later found to have relied heavily on Boeing's self-assessment of the system's risk. The grounding, the longest in commercial aviation history for an airliner still in production, forced a rewrite of how regulators evaluate single points of failure in flight-control software and cost Boeing billions of dollars in compensation to airlines and victims' families.

How we know

The MCAS design flaw, its reliance on a single sensor, and the timeline of both crashes and the subsequent grounding are documented in a peer-reviewed case analysis published via PubMed Central, the National Institutes of Health's public full-text archive.

Sources

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Two Crashes Ground the Boeing 737 MAX Worldwide · History of Aviation · SourcedStory