Here's the summary for the wikipedia article you mentioned in your comment:

The Maneuvering Characteristics Augmentation System (MCAS) is a flight stabilizing feature developed by Boeing that became notorious for its role in two fatal accidents of the 737 MAX, which killed all 346 passengers and crew among both flights. Systems similar to the Boeing 737 MCAS were previously included on the Boeing 707 and Boeing KC-46, a 767 variant. On the 737 MAX, MCAS was intended to mimic the flight behavior of the previous generation of the series, the Boeing 737 NG. During MAX flight tests, Boeing discovered that the position and larger size of the engines tended to push the nose up during certain maneuvers. Engineers decided to use MCAS to counter that tendency, since major structural redesign would have been prohibitively expensive and time-consuming.

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