(Reuters) - U.S. District Judge Reed O'Connor should reject a "sweetheart" plea deal the Justice Department struck with Boeing ( BA ), relatives of 15 of the 346 people killed in two fatal 737 MAX crashes said on Thursday.

Late Wednesday, the planemaker finalized an agreement to plead guilty to a criminal fraud conspiracy charge and pay at least $243.6 million after breaching a 2021 deferred prosecution agreement.

Family members said in a court filing in Texas that they will submit a comprehensive objection to the plea deal by next week, arguing that there are a number of issues including its "outdated and misleading statement of facts," use of "inaccurate sentencing guidelines" and "ambiguous restitution commitment" by Boeing ( BA ).

The families cited O'Connor's statement in a February 2023 ruling: "Boeing's ( BA ) crime may properly be considered the deadliest corporate crime in U.S. history."

Boeing ( BA ) and the Justice Department did not immediately respond to requests for comment.

The planemaker allowed potentially risky work at its factories and did not ensure key airplane record-keeping was accurate or complete, the Justice Department said as it outlined why it believed Boeing ( BA ) had violated the 2021 deferred prosecution agreement.

Boeing ( BA ) on July 7 agreed in principle to plead guilty to conspiring to defraud the Federal Aviation Administration after the government said the planemaker knowingly made false representations about key software for the 737 MAX.

The Justice Department said in May that Boeing ( BA ) had breached its obligations in the agreement that shielded the planemaker from criminal prosecution stemming from misrepresentations about a key software feature tied to fatal 737 MAX crashes in 2018 and 2019 in Indonesia and Ethiopia.

The Justice Department has a separate criminal probe ongoing into the Alaska Airlines jet that was missing four key bolts.

As part of the guilty plea deal, Boeing ( BA ) agreed to pay the maximum fine of $487.2 million and the DOJ recommended the court credit its previous 2021 payment of $243.6 million against that.

The deal also imposes an independent monitor, who will have to publicly file annual progress reports, to oversee the firm's compliance.

The families also raised concerns about the plea deal's failure to require Boeing ( BA ) to acknowledge that its "crime killed 346 people" and its implicit "exoneration of Boeing's ( BA ) then-senior management" and "unexplained calculation" of the $243.6 million fine.

The families also argued O'Connor rather than the Justice Department should select the independent monitor.