In a sign of how the credibility of the Federal Aviation Administration has been undermined in recent weeks, House Transportation Committee Chairman Peter A. DeFazio on Tuesday said “independent, third-party” reviewers must confirm that software and other fixes for Boeing’s 737 Max 8 jets are sufficient before the FAA allows the planes to fly again.

“The traveling public needs assurances that the FAA will only recertify the aircraft for flight if and when the FAA, outside safety and technical experts, and pilots agree the aircraft is safe to fly,” DeFazio (D-Ore.) said.

Those safety assurances are usually provided by the FAA itself. But the crashes of two Boeing 737 Max 8 jets in less than five months, killing 346 people in Indonesia and Ethiopia, have raised questions about the process Boeing and the FAA used to certify the planes were safe and the aircraft’s automated features were sufficiently understood by pilots.

The independent review, which DeFazio said has bipartisan support, should evaluate whether Boeing’s fixes are “comprehensive” and if “pilots have the information and training they need to fly these aircraft safely.” DeFazio said later this week he will also “submit document requests to the FAA and Boeing to drill down into key certification decisions regarding the Max.”

An FAA spokesman said the agency had not yet seen DeFazio’s formal request and had “no basis to comment.” Boeing did not immediately comment on DeFazio’s statement, but a spokesman said the company “is working with the authorities to evaluate new information as it becomes available” and has worked with the FAA, Transportation Department, pilots, airlines and others “for decades to make flying the world’s safest mode of transportation.”

The FAA was among the last civil aviation authorities to ground the planes after the crash in Ethiopia earlier this month, with agency officials saying they lacked the data needed to act. In the wake of the disasters, international aviation safety authorities have not been as deferential to the FAA, which has had a vital role in the United States’ exceedingly safe aviation record.

“I expect that our work will shed light on any deficiencies in the certification of aircraft in the United States and we will ensure that all lessons are applied and affect changes to improve the safety of our air transportation system and, hopefully, other nations’ as well,” DeFazio said.

Boeing has in recent days been showing pilots software fixes that would change the way some of the Max jets’ automated safety features behave and what information they rely on.

Pilots in the October crash in Indonesia appeared to struggle against an automated feature known as MCAS, which is designed to push the nose of the plane down if an external sensor detects the plane may be stalling, according to a preliminary report. The fixes, among other things, will stop the plane from relying on data from a single outside sensor, and temper how much the anti-stall feature would push the nose downward, the company said.

The Justice Department’s criminal division is looking into the Max jets; the Transportation Department’s inspector general is investigating the way they were certified; Transportation Secretary Elaine Chao has created an “expert special committee” to review certification procedures for the planes; and Congress is investigating and planning several hearings, including one Wednesday.

DeFazio’s committee is investigating the FAA’s certification of the plane, including the “roles and responsibilities” of the FAA and Boeing, he said.

Congress has, for many years, instructed the FAA to hand over more of its safety oversight responsibilities to companies such as Boeing. A stated goal was to increase efficiency at the agency, which critics within the industry and on Capitol Hill said was too slow in certifying the extraordinarily complex aircraft, slowing economic growth.

DeFazio’s transportation committee is also probing “how the safety critical systems that did not exist on prior 737 models were tested, evaluated, and assumed to be safe” and “why the Max was certified without requiring additional pilot training, among other things,” DeFazio said.

DeFazio asked the Transportation Department’s inspector general to investigate how the FAA evaluated new features on the planes, including “sensors and software, pilot training programs and manuals, and how new features were communicated to airlines, pilots, and foreign authorities.”

He “also requested that the Inspector general provide us with status reports on any corrective actions undertaken by the FAA since the first accident and whether pilot training is adequate before the Max returns to revenue service."