The chief executive of Ethiopian Airlines told the Wall Street Journal in an interview published today that he had reason to believe that software intended to prevent Boeing 737 MAX aircraft from stalling in flight had been activated aboard Ethiopian Airlines Flight 302 shortly before its crash. CEO Tewolde Gebremariam said that “to the best of our knowledge,” the Maneuvering Characteristics Augmentation System (MCAS) for stall prevention was active at the time of the crash.

This is the first time anyone connected to the Flight 302 investigation has specifically referenced the flight software as being involved. Ethiopian and French investigators had noted similarities in flight data to that of the ill-fated Lion Air Flight 610, a crash that was determined to be at least partially caused by the MCAS software’s malfunction due to a faulty sensor input. Investigators also cited the Flight 302 crew’s lack of training on how to shut the MCAS system down in the critical moments before the crash.

Gebremariam did not share what details he had received that led to his conclusion. But he did say that it would be difficult for Boeing to restore trust in the 737 MAX aircraft’s safety, and he was critical of Boeing’s failure to do more to inform airlines of the changes in operation related to MCAS when it was introduced. “In retrospect I would have expected them to have been more transparent on the MCAS, the technicalities of the MCAS, what it does and what it doesn’t do,” he told The Wall Street Journal. And after the first 737 MAX crash in Indonesia, the CEO said, “more should have been done from the Boeing side in terms of disclosure, in terms of coming up with strong procedures, stronger than what they gave us.”

Despite concerns about the future safety of the 737 MAX, Gebremariam did not say that Ethiopian Airlines would cancel its remaining orders for the aircraft, as Garuda Indonesia did last week.

Boeing is preparing to send out a software update to MCAS, which will include a “disagree light” indicator on the 737’s digital cockpit display when there is a difference between angle of attack readings from the aircraft’s sensors. That feature was previously offered as an add-on option. The new patch will also add redundancy in sensor checks to MCAS’ stall prevention feature and disable the stall correction in the event of a sensor failure or a difference in inputs. This update is expected to be made mandatory by the Federal Aviation Administration for all 737 MAX aircraft by the end of April.