In a rare move, a federal district judge on Thursday rejected Boeing’s proposed agreement with the Justice Department to plead guilty to conspiracy to defraud the federal government in connection with two fatal 737 Max crashes, according to court documents.

The plea agreement, reached in July, has been a flashpoint for controversy. It would have required Boeing to admit to deceiving the Federal Aviation Administration about critical safety issues tied to a flight control software implicated in both accidents. The crashes, a Lion Air flight in 2018 and an Ethiopian Airlines flight in 2019, killed a total of 346 people.

Judge Reed O’Connor, of the Northern District of Texas, raised concerns on several levels about how the agreement was handled, including a question about the independent monitor who was to determine if Boeing was abiding by the terms of the agreement. All parties have 30 days to decide how to proceed.

The proposed agreement included a fine of up to $487 million, credits for prior payments that could significantly reduce the penalty, and a three-year probation period during which Boeing would invest $455 million in safety measures.

Lawyers for some victims’ families have staunchly opposed the plea deal, arguing that it inadequately holds Boeing, and especially its executives, accountable for the tragedies.

Paul Cassell, an attorney representing the families, hailed the ruling as a victory.

“Judge O’Connor’s emphatic rejection of the plea deal is an important victory for the families in this case and, more broadly, for crime victims’ interests in the criminal justice process,” Paul G. Cassell, a lawyer for the victims, said in a statement.

Boeing did not immediately respond to a request for comment, nor did the Justice Department.

This is a breaking news story. Check back for updates.