WASHINGTON — Boeing’s chief executive faced the grieving relatives of two deadly crashes of its 737 Max jet at an emotional congressional hearing on Tuesday, as senators pummeled him with questions about whether the company should have grounded the plane before the second accident.



At times looking shaken, the executive, Dennis A. Muilenburg, said that if he could do it over again, he would have acted after the first crash, off the coast of Indonesia last October. “If we knew everything back then that we know now, we would have made a different decision,” he testified. He said Boeing officials had asked themselves “over and over” again why they didn’t ground the plane sooner.

“I think about you and your loved ones every day,” Mr. Muilenburg told the families, who at one point stood behind him holding up large photographs of the dead.

Still, Mr. Muilenburg acknowledged for the first time that he knew before the second crash that a top pilot had voiced concerns about the plane while it was in development.

The admission will most likely lead to more questions about why Boeing did not act more decisively before that crash, of Ethiopian Airlines Flight 302, on March 10.

Two days later, Mr. Muilenburg called President Trump to defend the safety of the Max. The plane was grounded, however, on March 13, although the United States waited longer than most countries to act.