Ms. Chao stressed that the F.A.A. sets safety standards that manufacturers must meet while developing aircraft. The certification process, she said, “is, of course, subject to oversight and supervision by the F.A.A.”
When asked by the subcommittee’s chairwoman, Senator Susan Collins, Republican of Maine, about concerns that the arrangement “sacrifices potentially the safety of the traveling public,” Ms. Chao said that the possibility was “troubling.”
Mr. Elwell, during his hearing, said that the F.A.A. initially oversaw certification for the software, but delegated more authority over time, “when we had the comfort level” that the Boeing employees were knowledgeable enough about the system.
Mr. Elwell later said that practice was “part of the fabric of what we’ve used to become as safe as we are today” and that without it, the F.A.A. would need 10,000 more employees and $1.8 billion for its certification offices.
Boeing has defended the process, saying the plane adhered to all F.A.A. safety rules.
A Boeing official cautioned against drawing any definite conclusions until more is known. “In general, the process has worked and continues to work, and we see no reason to overhaul the process,” this official said, speaking on the condition of anonymity because of the investigations.
The Boeing official said that in most accidents, many things go wrong. Based on what is known about the crashes in Indonesia and Ethiopia, Boeing said it felt that MCAS was in need of updating.
“We’ve seen two accidents now and we believe it is appropriate to make that link in the chain more robust,” the official said.