Boeing will plead guilty to a criminal fraud charge stemming from two crashes of 737 Max jetliners that killed 346 people after the American government determined the firm had breached an agreement that had protected it from prosecution for more than three years, the US justice department has said.

US federal prosecutors gave Boeing the choice last week of entering a guilty plea and paying a fine as part of its sentence or facing a trial on the felony criminal charge of conspiracy to defraud the United States.

Prosecutors accused the American aerospace giant of deceiving regulators who approved the plane and pilot training requirements for it.

The plea deal, which still must receive the approval of a federal judge to take effect, calls for Boeing to pay an additional 243.6 million dollar (£190 million) fine.

That was the same amount it paid under the 2021 settlement that the justice department said the company breached.

An independent monitor would be named to oversee Boeing’s safety and quality procedures for three years. The deal also requires Boeing to invest at least 455 million dollars (£355 million) in its compliance and safety programmes.

The plea deal covers only wrongdoing by Boeing before the crashes, which killed all 346 passengers and crew members aboard two new Max jets.

It does not give Boeing immunity for other incidents, including a panel that blew off a Max jetliner during an Alaska Airlines flight in January, a justice department official said.

The deal also does not cover any current or former Boeing officials, only the corporation. In a statement, Boeing confirmed it had reached the deal with the justice department but had no further comment.

In a court filing on Sunday night, the justice department said it expected to file the written plea agreement with the court by July 19.

Lawyers for some of the relatives of those who died in the two crashes have said they will ask the judge to reject the agreement.

Paul Cassell, a lawyer for some of the families, said: “This sweetheart deal fails to recognise that because of Boeing’s conspiracy, 346 people died. Through crafty lawyering between Boeing and DoJ, the deadly consequences of Boeing’s crime are being hidden.”

US federal prosecutors alleged Boeing committed conspiracy to defraud the government by misleading regulators about a flight-control system that was implicated in the crashes, which took place in Indonesia in October 2018 and in Ethiopia less five months later.

As part of the January 2021 settlement, the justice department said it would not prosecute Boeing on the charge if the company complied with certain conditions for three years. Prosecutors last month alleged Boeing had breached the terms of that agreement.

The company’s guilty plea will be entered in US district court in Texas. The judge overseeing the case, who has criticised what he called “Boeing’s egregious criminal conduct”, could accept the plea and the sentence that prosecutors offered with it or he could reject the agreement, likely leading to new negotiations between the justice department and Boeing.

The case goes back to the crashes in Indonesia and in Ethiopia. The Lion Air pilots in the first crash did not know about flight-control software that could push the nose of the plane down without their input. The pilots for Ethiopian Airlines knew about it but were unable to control the plane when the software activated based on information from a faulty sensor.

The justice department charged Boeing in 2021 with deceiving FAA regulators about the software, which did not exist in older 737s, and about how much training pilots would need to fly the plane safely.

The department agreed not to prosecute Boeing at the time, however, if the company paid a 2.5 billion dollar (£1.95 billion) settlement, including the 243.6 million dollar fine, and took steps to comply with anti-fraud laws for three years.

Boeing, which blamed two low-level employees for misleading the regulators, tried to put the crashes behind it. After grounding Max jets for 20 months, regulators let them fly again after the Boeing reduced the power of the flight software.

Max jets logged thousands of safe flights and orders from airlines picked up, increasing to about 750 in 2021, about 700 more in 2022 and nearly 1,000 in 2023.

The company, based in Arlington, Virginia, has dozens of airline customers spanning the globe. The best customers for the 737 Max include Southwest, United, American, Alaska, Ryanair and flydubai.

That changed in January, when a panel covering an unused emergency exit blew off a Max during the Alaska Airlines flight over Oregon.

Pilots landed the 737 Max safely and no-one was seriously injured, but the incident led to closer scrutiny of the company.

The justice department opened a new investigation, the FBI told passengers on the Alaska plane that they might be victims of a crime and the regulator the FAA said it was stepping up oversight of Boeing.