A key sensor had been wrecked, possibly by a bird strike.
Flying faster than recommended, the crew struggled with MCAS.
The doomed flight crashed six minutes after take-off from Addis Ababa in clear conditions.
"If the preliminary report from the Ethiopian authorities is accurate, the pilots quickly identified the malfunction and applied the manufacturer's checklist".
Quoting a USA pilot, who declined to be named, Reuters reported that "power being left in take-off power while levelling off at that speed" may be a major factor responsible for the disaster. "I can't imagine a scenario where you'd need to do that".
Since the 737 MAX planes remain grounded worldwide and deliveries of new aircraft have been halted, the company has slashed production rate of the plane model from 52 to 42 airplanes.
The update intends to "eliminate the possibility of unintended MCAS activation and prevent an MCAS-related accident from ever happening again", he said. They found that a malfunctioning sensor sent faulty data to the Boeing 737 Max 8's anti-stall system and triggered a chain of events that ended in a crash so violent it reduced the plane to shards and pieces.
Pilots in both airplanes seem to have had trouble regaining control of the aircraft after the MCAS system pushed the nose of the jets down to keep them from stalling. In both cases, all crew and passengers on board were killed.
But data suggest they did not hold the buttons down long enough to fully counteract the computer's movements. Audible warnings - "Don't Sink" - sounded in the cockpit. It does not describe a specific trim setting for the pilots to achieve.
This time, the pilots countered MCAS more effectively.
According to the Federal Aviation Administration, Boeing is expected to submit its package of potential fixes for regulatory approval in the coming weeks.
It also confirmed that external sensors on the plane's nose fed erroneous information into the plane's flight control system. The co-pilot reported problems to air traffic control.
"This accident was not survivable", said the report. Data confirms the engines stayed at almost full power. Other pilots said the flight crew's actions were understandable given the chaotic situation.
Pilots interviewed by Bloomberg didn't agree completely about the factors.
The proper response to MCAS emergencies, Leeham Co analyst Bjorn Fehrm said, is to correct the risky nose-down "trim" using electronic thumb switches, then turn off MCAS and trim manually with the wheel.
"We've always been relentlessly focused on safety and always will be; it is at the very core of who we are at Boeing and we know we can always be better".
But it was too hard to move the wheel. We're also finalizing new pilot training courses and supplementary educational material for our global MAX customers. "This is key because it caused other issues during various phases of the climb including improperly activating the MCAS". The report did not address that.
The plane eventually pointed down by 40 degrees and the plane reached speeds of 575 miles per hour.