Two crashes five months apart, Lion Air Flight 610 and Ethiopian Airlines Flight 302, killed 346 people and grounded the 737 Max worldwide. This FRONTLINE investigation, produced with The New York Times, reconstructs how Boeing designed the MCAS anti-stall system, why pilots were never told it existed, and how the company pushed to keep new training requirements off the books to protect the plane's sales pitch as a quick, cheap upgrade from older 737s. Interviews with engineers, former Boeing employees, FAA officials, and journalists trace a shift inside the company after its merger with McDonnell Douglas, from an engineering-driven culture to one measured by stock price and shareholder returns. Flight data, cockpit recordings, and internal documents show the FAA delegating large parts of its own safety oversight back to Boeing itself. The film lays out, step by step, how a single faulty sensor could repeatedly push both planes into fatal nosedives, and how warnings from engineers and even some pilots went unheeded before the second crash.