Boeing’s chief executive said on Sunday that the company made a “mistake” in how it handled a cockpit warning light on the 737 Max. Dennis Muilenburg, the executive, made the comments while addressing reporters on the eve of the Paris Air Show, one of the most important sales events for aircraft manufacturers around the world.

When Boeing began delivering the Max to airlines in 2017, the company believed that the light was operational on all the jets. But after the Max began flying that year, engineers at the company learned that the warning light would work only if a carrier had purchased a separate cockpit indicator.

Most Max customers, including Lion Air and Ethiopian Airlines, did not buy the separate indicator. That left many airlines without a functional warning light.

The light alerts pilots of a disagreement between two sensors that measure which direction the plane is pointed. Preliminary investigations suggested that problems with these so-called angle-of-attack sensors contributed to the crashes of two jets, a Lion Air flight last October and an Ethiopian Airlines flight in March, in which 346 people died.