The Maneuvering Characteristics Augmentation System (MCAS) is a flight stabilizing program developed by Boeing that became notorious for its role in two fatal accidents of the 737 MAX, which killed all passengers and crew on both flights, 346 people in total. MCAS was first used on the Boeing KC-46 Pegasus military air tanker to balance fuel loads, but the aircraft, which was based on the Boeing 767, allowed pilots to assume control of the aircraft.[1]