On October 29, 2018 at 6:20 AM, Lion Air Flight 610 took off from Jakarta, Indonesia

Indonesia-based Lion Air was flying Boeing’s 737 Max 8, the US aerospace manufacturer’s cutting-edge new plane, for a domestic flight

Immediately after takeoff, its pilots complained of “a flight control problem”

Twelve minutes later, the plane crashed into the Java Sea, killing all 189 passengers aboard

Five months later, an Ethiopian Airlines flight took off from Addis Ababa, Ethiopia, for Nairobi, Kenya, also flying a 737 Max 8

Within a minute, pilots reported issues controlling the plane

Five minutes later, it crashed into the ground at 700+ miles per hour, killing all 157 passengers

Aviation experts cited a device known as a Maneuvering Control Augmentation System (MCAS) as a contributing factor in both crashes

Amid the ensuing backlash, every country grounded its Boeing 737 Max fleets, plunging Boeing into a crisis

Now, following a disastrous mid-flight accident over Oregon, the plane is back in the headlines

Boeing is the world’s largest commercial aerospace manufacturer by market cap

Its flagship class of planes is the 737, which, since its debut in 1967, has become the best-selling airplane class ever

In 2006, it began considering a new model to succeed its then-current version, the 737NG

Boeing debated whether to build a new version of the 737 or create a new class of planes

Then in December 2010, Boeing’s competitor, Airbus, announced its new class of planes

Worried Airbus would out-compete it, Boeing began building a new version of the 737: The Max

In August 2011, Boeing announced it would create three versions of the Max – the 7, 8, and 9 – which would differ based on their size and other performance metrics

Crucially, each Max version was designed to be very similar to the 737NG, meaning that pilots and aircrews wouldn’t have to go through comprehensive training to learn how to fly them

Yet structurally, the Max had notable differences from the NG, including stronger engines that were positioned at different positions of the plane

That created different aerodynamics, including the tendency for the plane’s nose to tilt upward

Yet rather than totally redesign the plane, Boeing installed MCAS, which automatically adjusted the plane’s nose to keep it stable

In theory, MCAS worked in the background, meaning the plane’s pilots would never notice it

MCAS was designed to respond to a single sensor

That meant that if one of its two sensors malfunctioned, the MCAS system could wrongfully kick in, taking control of the plane from the pilots

The pilots could manually override that system, but doing so presented its own difficulties

The Lion Air and Ethiopian Airlines crashes showed that design flaw to be fatal: In both instances, MCAS incorrectly kicked in, leading to confusion, panic, and ultimately fatal crashes

Following the second crash, the world’s 737 Max-8 fleets were grounded, costing Boeing billions in lost revenue, lawsuits, and fines

Subsequent investigations revealed that an internal US federal report had predicted up to 15 Max crashes over a 30-40-year span – yet the US had let it fly

US regulators soon accused Boeing of having concealed crucial details about MCAS, resulting in information being absent from airplane manuals and pilot-training materials

The US said Boeing purposefully withheld that information to make the Max and its predecessor appear more similar than they actually were

That allowed airlines to use the same pilots for both NGs and 737s, saving them money and making the Max a more sellable plane

In 2021, Boeing paid $2.5B to settle related claims

The US approved the Max to fly again on November 18, 2020, almost two years after the second crash, and most other countries followed shortly after

The Max has since gone on to become Boeing’s best-selling model, and 76% of the company’s outstanding orders are for it

Yet another blow to Boeing came last week when a Max 9 flying from Oregon to California suffered a mid-flight blowout, exposing a gaping hole in its fuselage

No one was seriously injured, but the plane was brand new, raising concerns about inherent flaws in the Max

Several airlines have since attested to finding loose bolts on Max 9s

As another investigation begins, hundreds of 737 Maxs remain stuck on the ground once again

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