Families of the 157 victims,regulators and travellers around the world are waiting for clues to the accident after the new Boeing jet crashed six minutes after take-off.
Ethiopia released its first report on last month's fatal crash of the flight from Addis Ababa,as US aviation regulators announced a new safety review of the Boeing's grounded 737 Max planes.
People close to the Ethiopian investigation have said the anti-stall software – which automatically pushes the aircraft's nose down to guard against a loss of lift – was activated by erroneous'angle of attack'data from a single sensor.
The investigation has now turned towards how MCAS was initially disabled by pilots,in line with part of a cockpit checklist procedure,but then appeared to start working again before the jet plunged to the ground,the people said.
Officials briefed on the matter said a key question is when did the pilots at the helm of the Ethiopian Airlines 737 MAX disengage the MCAS system and did they do it too late to regain control of the plane.
Two people briefed on the matter said the system is not designed to resume operations unless the crew acts and the crew may have unintentionally re-engaged the system as it desperately tried to pull the plane out of its nose-down descent.
They cautioned the data was still being reviewed and that the findings were preliminary.