An anti-stall system that investigators believe led to the fatal crash of a Boeing 737 MAX 8 in October had been activated on the Ethiopian Airlines plane that plummeted under similar circumstances this month, the carrier’s CEO said Monday.

“To the best of our knowledge,” the Maneuvering Characteristics Augmentation System, or MCAS, was on during the doomed March 10 flight, which killed all 157 people aboard, Tewolde Gebremariam told the Wall Street Journal.

Gebremariam — who is not part of the official crash probe — didn’t elaborate on how he had made his determination about MCAS.

He doesn’t have access to the precise detail from the aircraft’s black boxes, but he has listened to tapes of radio communications between the cockpit and controllers at Addis Ababa airport, from which the flight departed, the paper reported.

Gebremariam added that he wanted to wait for the investigation for conclusive evidence about the doomed, six-minute flight.