BANGKOK — Boeing faced new scrutiny on Tuesday over the crash of one of its planes into the sea off Indonesia last month, as airlines, pilots and regulators sought to determine whether the company had underplayed the complexity of a new emergency system suspected of having malfunctioned on the doomed jetliner.

Investigators have been focused on whether the plane, Lion Air Flight 610, crashed because the system, which is designed to pull the plane out of a dangerous stall, activated based on inaccurate data transmitted or processed from sensors on the fuselage.

The plane plunged nose down into the sea, killing all 189 people on board. The precise cause or causes of the crash remain unclear.

Boeing has been selling the model that crashed, the new 737 Max 8, as requiring little additional pilot training for airlines that already use the previous version of the plane. The 737 Max 8 is in a ferocious competitive battle with an update of the Airbus A320, and minimizing the costs of upgrading to the new model is one of the keys to winning orders from airlines.