In a bipartisan effort, senators on Thursday called for revisions to a significant defense bill following criticisms from crash investigators and the families of victims. Concerns were raised that the current legislation might reverse crucial safety reforms established after a tragic collision between an airliner and an Army helicopter over Washington, D.C., which resulted in 67 fatalities.

The National Transportation Safety Board (NTSB), victims’ relatives, and members of the Senate Commerce Committee have expressed that the bill, which the House moved forward on Wednesday, could compromise aviation safety in the United States. They highlighted that the proposed changes would permit the military to operate in a manner similar to before the devastating January crash, the most lethal in over 20 years.

Senators Maria Cantwell, a Democrat, and Ted Cruz, the Republican Chairman of the Commerce Committee, proposed two amendments on Thursday. Their aim is to remove the contentious helicopter safety clauses and substitute them with a previous bill they introduced to enhance safety standards. However, it remains uncertain whether Republican leaders will permit alterations to the National Defense Authorization Act at this point, as it could delay its approval.

“We have a responsibility to the families to enact genuine safety advancements, rather than providing the Department of Defense with larger loopholes to exploit,” the senators stated.

The current bill contains provisions that would exempt military helicopters from using the Automatic Dependent Surveillance–Broadcast (ADS-B) system to transmit their locations while flying through the busy airspace around the nation’s capital, a requirement the Federal Aviation Administration (FAA) implemented in March. NTSB Chairwoman Jennifer Homendy described the bill as a “significant safety setback,” warning that it could lead to another similar disaster.

“It represents an unacceptable risk to the flying public, to commercial and military aircraft, crews and to the residents in the region,” Homendy said. “It’s also an unthinkable dismissal of our investigation and of 67 families … who lost loved ones in a tragedy that was entirely preventable. This is shameful.”

Senate Majority Leader John Thune said he is looking into the concerns but thinks they can be addressed by quickly passing the aviation safety bill that Cruz and Cantwell proposed last summer.

“I think that would resolve the concerns that people have about that provision, and hoping — we’ll see if we can find a pathway forward to get that bill done,” said Thune, a South Dakota Republican.

The military used national security waivers before the crash to skirt FAA safety requirements on the grounds that they worried about the security risks of disclosing their helicopters’ locations. Tim and Sheri Lilley, whose son Sam was the first officer on the American Airlines jet, said this bill only adds “a window dressing fix that would continue to allow for the setting aside of requirements with nothing more than a cursory risk assessment.”

Homendy said it would be ridiculous to entrust the military with assessing the safety risks when they aren’t the experts, and neither the Army nor the FAA noticed 85 close calls around Ronald Reagan National Airport in the years before the crash. She said the military doesn’t know how to do that kind of risk assessment, adding that no one writing the bill bothered to consult the experts at the NTSB who do know.

The White House and military didn’t immediately respond Thursday to questions about these safety concerns. But earlier this week Trump made it clear that he wants to sign the National Defense Authorization Act because it advances a number of his priorities and provides a 3.8% pay raise for many military members.

The Senate is expected to take up the bill next week, and it appears unlikely that any final changes will be made. But Congress is leaving for a holiday break at the end of the week, and the defense bill is considered something that must pass by the end of the year.