If the nose of the Boeing Max 8 model rises, threaten

ning a midair stall, the MCAS system automatically points the plane’s nose down

to gain speed needed to stay aloft. Boeing added larger, more fuel-efficient engines to upgr

ade the existing 737 airframe to compete with European rival Airbus. The new engines are positioned close

r to the fuselage, changing the aircraft’s aerodynamics and pushing the nose up in certain conditions.

Boeing created MCAS to make the new Max planes handle more like previ

ous versions of the 737, a popular model used by airlines around the world. Some in the aircra

ft industry, including pilots, have said Boeing did not provide adequate notice of the new plane’s flight ch

aracteristics or how to shut off the new anti-stall device if necessary. A group of pilots in

dependently compiled and circulated a 13-page manual about the new system. Oth

ers have said Boeing provided adequate notice of the changes and how to disable MCAS.

The version of MCAS installed on the Ethiopian Airlines pl

ane had relied on information from one sensor that sent back bad information.

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