The chairman of a House panel charged at a hearing Wednesday that delegating some aspects of safety certification to Boeing is "not working as Congress intended" and declaring MAX jets safe to fly has created a "credibility problem" for the Federal Aviation Administration (FAA) in view of two fatal crashes.

"Congress must find answers to what happened in these two accidents," said Representative Rick Larsen, a Democrat from Washington state and chairman of the Aviation Subcommittee. "The committee will not hesitate to act to assure the safety of the US air system."

Boeing MAX jets were grounded worldwide following crashes March 10 in Ethiopia and Oct 29, 2018, in Indonesia that killed a total of 346 passengers and crew.

Preliminary investigations suggest the aircraft's Maneuvering Characteristics Augmentation System (MCAS), an automated anti-stall device, apparently forced the noses of Lion Air and Ethiopian Airlines flights down and into a fatal plunge when it erroneously determined the aircraft were about to stall.

Critics have said the FAA relied too heavily on Boeing's engineers when certifying the aircraft. But Daniel Elwell, acting administrator of the federal regulatory agency, said a review of the plane's safety took five years to complete, and while the regulatory agency relied on Boeing for technical details, the FAA made the final decision.

He said he supported the idea of delegating "certain tasks and certain decisions" in the certification process to private employees, despite criticism that the practice has led to lax oversight. He said that the process by which Boeing company-paid employees inspected their own aircraft was "a good system".

Elwell said the FAA — not Boeing or any other agency — will decide when MAX jets can resume commercial flights.

"In the US, the 737 MAX will return to service only when the FAA's analysis of the facts and technical data indicate that it's safe to do so," Elwell testified. He did not say when that might occur.

Larsen said he wanted further details on the FAA's certification process, including Boeing's role in developing a pilot training program for the aircraft.

Congressman Peter DeFazio, a Democrat from Oregon, said pilot manuals for MAX jets failed to mention an anti-stall device and therefore may have contributed to the crashes. He said the FAA has begun to turn over documents requested by the subcommittee of the House Transportation and Infrastructure Committee, but Boeing has not yet provided any information.

"We've got to get to the bottom of this," DeFazio said. "I don't want anyone to think we're going to walk out of here today with all the answers. This is a very complex issue."

DeFazio said The Wall Street Journal reported that top FAA officials did not participate in the review of the anti-stall system.

"I'm not aware of an internal assessment that reaches that conclusion," Elwell said. But Elwell said he was not happy with the 13-month delay in initial reports of trouble with the anti-stall system and the FAA's learning about it.

"We will make sure software anomalies are reported more quickly," he said.

Elwell said details of the Indonesian crash were shared with the US Department of Transportation to determine its cause. "If we have robust oversight, it's a good system," Elwell said. "But it can always be better."

Representative Dina Titus, a Democrat from Nevada, said, "You were in bed with those you were supposed to be regulating, and that's why it took so long. That's the impression the public has and what we need to deal with."

Elwell said MAX jets were grounded in the US only when data, including radar tracks of the doomed aircraft, suggested a link between the two crashes. The FAA grounded the 737 MAX after China and nations around the world had pulled the planes from service.

Earlier on Wednesday, Senator Ted Cruz, Republican from Texas, told President Donald Trump's nominee to lead the FAA that he needs to be "outraged'' about how many people died in the crashes in Ethiopia and Indonesia.

At a hearing of the Senate Commerce, Science and Transportation Committee, Cruz told Steve Dickson to battle what Cruz called "bureaucratic inertia" that he said prevented the FAA from exercising stronger oversight.

Cruz accused the FAA of allowing a "serious breakdown in the certification process" of the 737 MAX jets.

"So, Mr. Dickson, I would ask you not to give in to the natural bureaucratic reaction to defend what happens," Cruz said. "But instead, ask seriously ... whether we could have prevented these crashes."

Dickson, a former Delta executive, was nominated in March to serve as the FAA's next administrator.