In 2010, Airbus announced it would introduce a more fuel-efficient version of its popular A320 jetliner. Within months, Boeing announced plans to upgrade its own 737 jets.
In designing the new 737 Max, Boeing tried to avoid a complete overhaul of its systems so that it could persuade regulators at the U.S. Federal Aviation Administration that there would be no need for expensive, time-consuming retraining for pilots.
That decision appears to have left the crew of the Lion Air jet that crashed in Indonesia in October, killing 189 people, without a full understanding of how to respond when faulty data led the flight control system to repeatedly push down the nose of the plane.
How we know: Our journalists interviewed engineers, former Boeing employees, pilots, regulators and congressional aides to understand some of the choices Boeing made as it developed the 737 Max.
The central problem: The Max’s enlarged engines had to be mounted differently, which had a destabilizing effect. A new, automatic flight control system was created to counter the possibility of stalls. It’s likely that the Lion Air pilots weren’t told about the new system — or how to handle it in an emergency.