Four weeks before a Lion Air jet plunged into the Java Sea in October, Congress passed little-noticed provisions that gave the plane’s maker, Boeing, even more power to oversee itself, demonstrating the company’s sway in Washington.

It was another victory in ­Boeing’s long-running, highly effective campaign to get the federal government to delegate more and more of the Federal Aviation Administration’s safety responsibilities to the company. It also was a reflection of the inherent difficulties of having a government workforce oversee the design and production of some of the world’s most sophisticated machines.

Federal investigators are scrutinizing whether the FAA failed to properly watch over Boeing, which has scrambled to make software fixes after two Boeing 737 Max 8 jets crashed within five months. But the obscure provisions in the new law show how advocates in Congress considered the process that certified the planes to be too cumbersome.

The U.S. manufacturing giant has spent decades building deep ties across Washington. President Ronald Reagan’s chief of staff, Kenneth M. Duberstein, sits on Boeing’s board of directors. So does Caroline B. Kennedy, President John F. Kennedy’s daughter and the former ambassador to Japan.

Boeing reported spending $15 million to lobby Congress, the FAA and other federal agencies last year, and it hired outside lobbyists to push the oversight delegation issue, according to disclosures filed with the Senate.

The provisions were part of a broader FAA funding and disaster relief bill that passed by wide margins and was signed by President Trump in October.

The law gives private companies more power over the rule books that describe what role the FAA has in approving designs. It also sets up an “advisory committee,” with industry representation, that establishes metrics the FAA must “apply and track.”

The debate over such changes has gone on for years. It offers a window into an oversight system that some critics say may have contributed to Boeing — and the federal government — missing potential software and hardware flaws in the Max jets and failing to mandate sufficient training information.

Proponents say distributing more oversight work to Boeing was necessary to increase efficiency at the FAA. But the trend may have unintended consequences for safety. The deaths of 346 people in the crashes of 737 Max 8 jets in Ethi­o­pia and Indonesia have created a crisis for Boeing and the FAA, even as investigators continue delving into the disasters’ causes. It remains unclear how the federal government will respond.

“In recent successive acts, Congress directed FAA to streamline certification, including increased delegation,” an FAA spokesman said. “With strict FAA oversight, delegation extends the rigor of the FAA certification process to other recognized professionals, thereby multiplying the technical expertise focused on assuring an aircraft meets FAA standards.”

Congress will hold a hearing Wednesday on federal aviation oversight with acting FAA administrator Daniel K. Elwell, who Trump recently said will be replaced by Stephen M. Dickson, a former Delta Air Lines pilot and executive.

Also testifying will be the Transportation Department’s inspector general, Calvin L. Scovel III, whose office has for years raised concerns about the FAA’s oversight of its delegation efforts. Investigators with Scovel’s office are probing the certification of the 737 Max, and the Justice Department’s criminal division also is looking into the aircraft.

But in an earlier hearing that seems frozen in time — before tragedy put the hard-charging manufacturer in crisis-management mode — the then-chief executive of Boeing Commercial Airplanes, Ray Conner, made the case for why the FAA should give up more of its traditional oversight functions and let his company handle them.

Conner cited competition from China and Boeing’s work on the 737 Max and other new aircraft that would benefit travelers and airlines, including by lowering fuel costs.

“The introduction of each airplane will also improve aviation safety as newer and safer airplanes with enhanced safety technologies replace older airplanes in the fleet,” Conner told the House Committee on Transportation and Infrastructure in 2015. “Of course, each airplane will have to be certified by the FAA, and the large volume of this work poses a significant challenge for the agency. I think that we could do more of the work . . . the FAA is doing today.”

At the direction of Congress, the FAA set up the certification system, known as the Organization Designation Authorization program, in 2005. It delegates power to a company unit inside Boeing that is supposed to do much of the detailed, technical legwork involved with finding whether a company is complying with safety standards. Proponents of the system said the FAA was understaffed and too slow to issue approvals, hampering economic growth. Boeing pays the workers, which the company said numbered 1,000 in 2015.

Critics, including some inside the FAA, said the agency would be ceding too much of its core safety mission — making sure Boeing’s planes are safe for the flying public — to the company. Some FAA officials worried the federal government was creating a classic fox-guarding-the-henhouse scenario.

“I still do think there is some power and influence when you are signing the paycheck,” Rep. Lois Frankel (D-Fla.) told Conner.

She pressed him on whether the company was arguing that certain parts of a plane’s design “should not have an inspection by an independent party.”

Conner said that was not the case. He put particular emphasis on the argument that the FAA should further cede control to Boeing in areas that are not as important for safety, such as for airplane “seats, lavatories, galleys,” bemoaning the “inordinate amount of time spent sometimes on seat certifications, on interior certifications.”

Passing control in some areas would free up the FAA so it “can be focused on those new technologies” that can be overseen with a more holistic, “risk-based approach” that concentrated more on gauging whether Boeing’s overall safety systems are solid, Conner said.

“I want to stress here too that we have worked very well with the FAA on moving toward this delegation. . . . We are moving in a positive direction,” Conner said. But, he said, “It is about speed.”

Conner received strong public backing.

“Too often we are seeing unnecessary regulatory burdens that do not serve to improve actual aircraft safety. It seems to be a process simply for the sake of process,” then-Rep. Bill Shuster (R-Pa.), who was chairman of the House Transportation Committee, said at the time.

Cresent Hardy, then a Republican congressman from Nevada, asked: “Instead of us telling you how to run your company and how we should restrict you, could you maybe elaborate a little bit on — tell us how regulations should be structured if you were in charge?”

“Government regulation too often, in the name of protecting the public, makes us less competitive — and actually does very little to protect the public,” said Rep. Tom Rice (R-S.C.), who thanked Conner “for American excellence in aviation and for employing so many thousands of the people in South Carolina.”

Rice added that Boeing has a “vested interest” in safety because “if we sacrifice safety in American aviation, then we won’t be competitive in that area very long.”

Sophie Seid, a spokeswoman for Rice, said the congressman “maintains his position that we need to use government resources effectively to prioritize flight safety.”

Conner retired from Boeing and now sits on the board of Alaska Airlines. A Boeing spokesman said FAA regulations on delegating authority “ensure that Boeing employees serving in this capacity act independently on behalf of the FAA when performing in this role.”

A long-term FAA funding bill was delayed for years after that hearing, in part because Shuster was pushing to shift the nation’s air traffic control system out of government hands, a cause that was joined by Trump but that eventually foundered.

That slowed passage of proposals supporting Boeing’s call for greater authority. When Congress finally acted in the fall, it took an approach that was more expansive than what Conner and his congressional backers had emphasized at the hearing years before.

The changes were not limited to routine areas such as seats and bathrooms.

Experts familiar with the program had differing views on the implications of the law, with some saying it opened the door to abuse and others arguing that numerous safeguards remain that give the FAA final say on whether to certify that a new airplane is safe.

One of the provisions approved in October creates an “advisory committee” that does more than advise. The group can establish performance metrics the FAA “shall apply and track.”

One of the stated goals is “eliminating certification delays and improving cycle times” — how long it takes from the time an application is submitted until it’s approved.

Another potentially far-reaching provision affects what happens if a company like Boeing requests changes in its “procedures manual,” which sets out whether it is the FAA or the private firm that approves “technical data” and whether airworthiness standards are being met. Under the new law, the FAA must approve revisions to that manual if the company asks for them. The agency can undo those changes only after an inspection or investigation proves “the public interest and safety of air commerce” require doing so.

The law also seeks to address some concerns about the program, instructing the FAA to develop evaluation tools and make clear how many employees it would need to provide better oversight.

The Organization Designation Authorization program, or ODA, was based on an odd bureaucratic hybrid. There would be an ODA “holder,” the company applying to the FAA to certify its new aircraft can carry passengers — in this case, Boeing. Then there would be an ODA “unit,” made up of Boeing employees authorized to do some of the FAA’s certification work.

There was supposed to be a wall between the two. One was Boeing, the applicant; the other was Boeing, the FAA’s agent.

But in the years preceding the Oct. 29 Lion Air crash in Indonesia and the March 10 crash of a 737 Max 8 in Ethi­o­pia, the Transportation Department’s internal watchdog repeatedly pointed to flaws in the ODA system.

An internal report from the department’s Office of Inspector General in 2012 said its investigators interviewed front-line FAA safety officials who pointed to potential conflicts of interest. They said FAA managers were being judged on their “delivery of airplanes . . . which may conflict with advocating FAA’s position” on safety.

Investigators found evidence to back up internal allegations that key FAA managers “have not always supported . . . employee efforts to hold Boeing accountable.” They also pointed to concerns about a lack of transparency and “management having too close a relationship with Boeing officials.”

The inspector general’s audits in years since have continued to raise concerns, even as Boeing and others in the aviation industry continued to push to take a bigger role.

After the Ethio­pian Airlines crash, the FAA said its “aircraft certification processes are well-established and have consistently produced safe aircraft designs.” The 737 Max planes — which are grounded worldwide — followed the “standard” process, the agency said.

Boeing said the planes followed “the identical FAA requirements and processes” that governed previous planes.