Boeing has previously described a production pause - which could potentially affect staffing and suppliers - as possible but not a likely course of action. Shares of Boeing finished at US$331.06, down 3.8 per cent, extending losses from Friday's 6.8 per cent drop. The latest twists in the MAX crisis stem from a November 2016 instant message conversation involving Boeing's chief technical pilot for the 737, Mark Forkner, over the performance of the Manoeuvering Characteristics Augmentation System during a simulation. The MCAS is a flight-handling mechanism believed to be at the center of two MAX crashes, which led to the plane's grounding since mid-March. In both crashes, the MCAS pointed the plane sharply downward based on a faulty sensor reading, hindering the pilots' ability to control the aircraft after takeoff, according to preliminary crash investigations.