The pilots of the Ethiopian Airlines 737 Max that crashed last month killing 157 people correctly followed Boeing’s emergency instructions but were still unable to stop the plane’s nose repeatedly pointing down, investigators said.

In the final seconds before the crash, pilots tried desperately to right the plane by switching its anti-stall software on and off but to no avail. The jet hit an airspeed of 500 knots (575mph), well above its operational limits, before cockpit data recordings stopped.

The Ethiopian government said data from the plane’s recorders showed “repetitive uncommanded aircraft nose-down conditions” and said Boeing should review its aircraft control system.

The country’s transport minister, Dagmawit Moges, did not cite the aircraft’s controversial anti-stall system by name, but said: “The crew performed all the procedures repeatedly provided by the manufacturer but was not able to control the aircraft.”

The initial findings will intensify pressure on Boeing to explain and resolve the issues with its Max jets, the company’s newest airplanes, which have been grounded worldwide following two fatal crashes in five months.

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The Boeing jet crashed on 10 March shortly after takeoff from Addis Ababa. It was the second crash of a 737 Max after the Lion Air disaster in Indonesia in October, which killed 189 people.

Ethiopian Airlines said the report clearly showed that the pilots had followed procedures. “Despite their hard work and full compliance with the emergency procedures, it was very unfortunate that they could not recover the plane from the persistence of nosediving,” it said.

Ethiopian investigators said the full investigation to determine what other factors may have been involved could take up to a year.

While air investigation reports do not apportion blame, the Ethiopian inquiry has again highlighted the 737 Max control system. Indonesian investigations into the Lion Air crash have focused on Boeing’s anti-stall system, Mcas, new on the Max model of 737 aircraft.

After the news conference, Moges told the New York Times that the Ethiopian Airlines pilots “turned the Mcas on and off, but I can’t say how many times because we will find that out when we have the final report”.

Pilots on the Lion Air flight, which also crashed within minutes of takeoff, battled to keep the plane pointing upwards as Mcas forced the nose down. After that crash, Boeing issued instructions to pilots on how to override the Mcas system, but the Ethiopian crash report suggests they may not have worked.

On Thursday Boeing announced that new software would ensure that pilots will always have the authority to override the system if it is activated by faulty sensor data.

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“I’d like to reiterate our deepest sympathies are with the families and loved ones of those who lost their lives in the accident,” said Kevin McAllister, Boeing Commercial Airplanes president and chief executive. “We thank Ethiopia’s Accident Investigation Bureau [AIB] for its hard work and continuing efforts. Understanding the circumstances that contributed to this accident is critical to ensuring safe flight. We will carefully review the AIB’s preliminary report, and will take any and all additional steps necessary to enhance the safety of our aircraft.”

Boeing could be left liable for huge payouts to victims and airlines. Lawsuits relating to both disasters have already been filed in the US, and some pilots have complained that the new features in the Max were not the subject of more comprehensive retraining.

The manufacturer also faces an investigation by the US Department of Justice, with FBI involvement, into its development process, and Senate hearings into how the Federal Aviation Administration allowed it to self-certify parts of its aircraft.

The 737 is Boeing’s bestselling current model, with about 5,000 orders worth up to $600bn (£456bn), of which 300 planes have so far been delivered to airlines. Both Ethiopian and Lion’s models had been in operation only for a matter of months before the crashes occurred.