The cause of the Ethiopian Airlines crash which killed 157 people has been revealed, according to reports.
It is believed the Boeing 737 Max suffered a damaged 'angle-of-attack' sensor upon takeoff from a foreign object which could have been a bird, ABC News reports.
This reportedly triggered erroneous data and the activation of an anti-stall system that sent the plane down on March 10 shortly after take off from Addis Ababa.
Boeing anti-stall software on the doomed jet re-engaged and pushed the jet downwards after the pilots initially turned it off due to suspect data from an airflow sensor, two sources said.
It was not immediately clear whether the crew intentionally re-deployed the MCAS system, which was designed to push the nose of the 737 MAX down to prevent a stall.
The pilots were not able to get control of the plane back, sources told ABC News.
Passengers from more than 30 nations were on board the aircraft.
Preliminary findings of an investigation into the crash are due to be released tomorrow morning by officials in Ethiopia.
Ethiopian Airlines crash investigators reach 'conclusion' using black box data
Boeing's anti-stall software is at the centre of investigations into last month's Ethiopian Airlines crash and a Lion Air accident in Indonesia in October.
Last month's aircraft's flight data recorder (FDR) and cockpit voice recorder (CVR), or black boxes as they are often called, have been recovered and investigators are hoping they will shed light on the tragedy.
Investigators from France and America are assisting in the probe.
Safety experts stress accidents are usually caused by a combination of factors and the probe is at an early stage.
No significant new technical issues have so far emerged in the Ethiopian investigation beyond those already being addressed by Boeing through updated software in the aftermath of the Lion Air crash, a person familiar with the findings told Reuters.
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 the MCAS system 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, sources said.
149 passengers and eight crew members were killed when the plane went down just six minutes after take-off.
Boeing is working to submit an upgrade of the software to the US regulators in a couple of weeks and adding extra training.
Boeing's fastest-selling 737 MAX jet, with orders worth more than $500 billion at list prices, has been grounded globally by the Federal Aviation Administration (FAA).
But airlines are still allowed to fly planes without passengers to move them to other airports, it is understood.
The UK Civil Aviation Authority announced that it had banned the jet from UK airspace and the European Aviation Safety Agency has suspended flights involving Boeing 737 Max 8 and 9.
