The Boeing 737 MAX was famously banned (grounded) worldwide for nearly two years (2019–2020) following two fatal crashes—Lion Air Flight 610 and Ethiopian Airlines Flight 302—which killed 346 people. The primary cause was a flawed flight control software system known as MCAS (Maneuvering Characteristics Augmentation System), which was designed to automatically push the plane's nose down to prevent a stall. Due to a faulty sensor, the system erroneously activated, and pilots were unable to override it because they had not been properly trained on its existence. While the aircraft returned to service in 2021 after extensive software fixes and pilot training, it faced a brief "partial ban" again in early 2024 after a "door plug" blew out of an Alaska Airlines MAX 9 during flight. This second incident was attributed to quality control failures at Boeing's assembly plant rather than the MCAS software, but it reignited global safety concerns and intense regulatory scrutiny.