Three Democratic senators introduced legislation Tuesday to tighten federal oversight of aircraft manufacturers following the deadly crashes of two Boeing 737 Max jets, saying the current setup allowed the company to prioritize profits over safety.

The legislation, the most sweeping so far introduced in the wake of the crashes that killed 346 people, boils down a response to the view among some key lawmakers that the system for approving new aircraft is badly broken. It targets the Federal Aviation Administration’s relationship with industry, which lawmakers have said has been revealed to be too cozy.

“Left to its own devices, the aviation industry has put corporate profits before consumer safety,” said Sen. Richard Blumenthal (D-Conn.), the effort’s lead sponsor. “When safety is inexcusably compromised like it was by Boeing — certification rushed, whistleblowers gagged, critical information deliberately concealed, speed and earnings prioritized — lives are tragically lost and families devastated.”

The bill would strengthen the FAA’s oversight of engineers who are employed by companies like Boeing but work on the government’s behalf conducting safety approvals, empowering the FAA’s leaders to set standards and requiring regular independent audits.

Lawmakers in the House and Senate have been investigating the October 2018 and March 2019 crashes, with an eye to whether aviation safety laws ought to be changed. They have focused in particular on a system called Organization Designation Authorization, or ODA, which allows aviation companies to create special units that do safety work on behalf of the FAA.

Critics of the system say the units don’t act as a proper check on the companies and can leave manufacturers like Boeing essentially grading their own homework. But a panel of safety experts convened by Transportation Secretary Elaine Chao warned against attempts to overhaul the system, saying changes could undermine collaboration between industry and government, undermining safety rather than bolstering it.

The legislation is also sponsored by Sens. Tom Udall (D-N.M.) and Edward J. Markey (D-Mass.), and has the support of the Air Line Pilots Association and other major transportation unions. But the bill’s ultimate prospects of success in the Republican-controlled Senate are not clear.

Udall said the crashes proved that aircraft manufacturers can’t be relied on to guarantee safety.

“The American people expect the FAA to be tough, independent and uncompromising when it comes to their safety, and this new bill would restore integrity in the FAA’s certification process,” he said.

The three sponsors of the legislation are members of the Senate Commerce Committee, which oversees aviation. Sen. Maria Cantwell (Wash.), the committee’s top Democrat, has introduced other legislation that is designed to address the challenges posed by new cockpit technology and is backing a proposal to help the FAA attract new employees with technological expertise.

Lawmakers in the House are continuing their investigation, but leading Democrats on the Transportation Committee have said they also expect to introduce legislation. Committee Chairman Peter A. DeFazio (D-Ore.) said recently that leaving the current system intact would be “the height of irresponsibility.”

An FAA spokesman said the agency doesn’t comment on legislative proposals.

Boeing declined to comment other than saying it was committed to working with the FAA to promote safety.

One investigation into the design of the Max concluded that federal regulators didn’t have all the information they might have needed to catch safety problems with an automated feature implicated in both crashes. And Boeing emails released by House investigators show company employees trying to downplay the significance of the feature to regulators, apparently to avoid costly training on it being required.

The bill would give the FAA administrator the power to set educational and experience requirements for engineers working at the company safety review units and require him to approve individual employees to do work on behalf of the agency. It would also undo some changes in a 2018 law that gave more authority the companies involved in the system and ban companies from assessing the engineers’ performance in terms of aircraft delivered.

The legislation would also create a commission to review the system as a whole.

The proposal includes other provisions, including a section aimed at giving American authorities a greater say in training requirements for planes made in the United States but being operated by foreign airlines. The bill also seeks to bolster whistleblower protections for people working in the aviation industry.