Boeing said Monday that it didn’t “intentionally or otherwise deactivate” the disagree alert on its 737 Max jets.
Southwest said it did not know about the deactivation of the disagree alert, which warns pilots about malfunctioning sensors, until after the Lion Air flight crash in Indonesia, and said that Boeing indicated in its manual that the disagree lights were functional.
“Boeing included the disagree alert as a standard feature on the Max, although this alert has not been considered a safety feature on airplanes and is not necessary for the safe operation of the airplane,” the company said. “Boeing did not intentionally or otherwise deactivate the disagree alert on its Max airplanes.”
The feature is an alert that lights up in the cockpit if a plane’s angle-of-attack sensors transmit incorrect data about the pitch of the plane’s nose.
“The disagree alert was intended to be a standard, stand-alone feature on Max airplanes. However, the disagree alert was not operable on all airplanes because the feature was not activated as intended,” the company said.
The Max jet’s anti-stall software was implicated in the crashes in Ethiopia and Indonesia that killed a total of 346 people. The grounding of the jets since March has forced major airlines to cancel thousands of flights through the summer.