WASHINGTON — The head of the Federal Aviation Administration faced sharp questioning from Congress on Wednesday as he sought to defend the agency’s certification of the Boeing 737 Max, and its decision not to ground the plane after a first deadly crash last year.
A second plane crashed under similar circumstances five months later, leading to the grounding of the Max and throwing Boeing into the worst crisis in its history.
After the first accident in October 2018, an analysis by the F.A.A. determined that the plane was likely to crash again if regulators did not act, according to a federal document presented during a House Transportation Committee hearing on the two 737 Max crashes.
“The F.A.A. must fix its credibility problem,” said Representative Rick Larsen of Washington, who along with Representative Peter DeFazio of Oregon have been aggressive in their scrutiny of the F.A.A. and its role in the Max crashes.
The F.A.A.’s analysis found that without government intervention, the Max would likely crash 15 times over the 45 years that it was expected to fly, potentially killing more than 2,900 people. The analysis was reported earlier by The Wall Street Journal.
“Despite its own calculations, the F.A.A. rolled the dice on the safety of the traveling public and let the plane continue to fly,” Mr. DeFazio said.
By the time the F.A.A. conducted the review last December, however, it had already taken action that it assumed would mitigate that risk.
In November, about a week after the Lion Air accident off the coast of Indonesia, the regulator issued a directive instructing pilots of the 737 Max to use a common emergency procedure to deal with the erroneous activation of software, which was a factor in the crash.
The F.A.A.’s administrator, Stephen Dickson, maintained that the agency was independent and that the aircraft certification process was fundamentally sound.
“The system is not broken,” he said.
The analysis, known as a transport aircraft risk assessment methodology, “is one of several safety tools regularly used by the F.A.A. to analyze safety issues,” an F.A.A. spokesman, Lynn Lunsford, said in a statement.
The F.A.A. relied on the review and on the investigation of the Lion Air crash “to validate the agency’s immediate decision” to release a directive reminding pilots of the emergency procedure, he said.
In a statement, a Boeing spokesman, Chaz Bickers, said the actions that the F.A.A. and Boeing took after the first crash “were fully consistent with the F.A.A.’s analysis and established process.”
However, in March, there was a second deadly crash involving the Max, this time in Ethiopia. In all, 346 people were killed in the two crashes.
The 737 Max has been grounded around the world since shortly after that crash. The crisis has roiled Boeing and the global aviation industry as the process of getting the plane flying again has dragged on.
Mr. Dickson said that the F.A.A., not Boeing, would determine when the Max would fly again, which will not happen until 2020. Boeing has encountered repeated delays in its efforts to return the plane to service.
The three airlines that fly the Max in the United States — American Airlines, Southwest Airlines and United Airlines — have all canceled Max flights into March. The F.A.A. does not expect to issue instructions for new pilot training on the Max until January.
The hearing was the fifth held by the House transportation committee as it investigates the design, certification and crashes of the Max. Later on Wednesday, the committee will hear from Ed Pierson, a former Boeing employee who raised concerns about the production of the Max before the first crash.
David Gelles reported from Washington and Natalie Kitroeff from New York.