NEW YORK (AP) — Boeing says it didn’t tell pilots and airlines that a safety alert on its 737 Max jets was not working until after one of the planes crashed in Indonesia last year.

The safety alert, called an “angle of attack” (AOA) indicator, tells pilots if a sensor is transmitting bad data. It was designed to warn pilots about the kind of sensor malfunction that occurred in the crash in Indonesia and another five months later in Ethiopia. It had been operational in previous versions of the 737, but was switched off in the 737 Max.

Boeing said Sunday that the planes could be flown safely without the alert, but said it will be included in the 737 Max before the planes are flown again.