New, tough questions are being asked about Boeing's 737 Max, the fastest-selling jet in the iconic company's history. After being involved in two crashes that killed 346 people, the troubled commercial aeroplane was forced to make an emergency landing this year after a door plug blew out and a passenger was nearly sucked out of it. This special update to an award-winning investigation from PBS Frontline and The New York Times investigates the plane's commercial pressures, flawed design and failed oversight.