Boeing chief executive Dennis Muilenburg came under intense grilling at the Senate Commerce Committee Tuesday, his first public questioning by Congress since Lion Air flight 610 crashed into the Java Sea exactly one year ago.

Muilenburg told senators he was open to reassessing how much responsibility his company takes on for guaranteeing that its new planes are safe as he testified about two deadly crashes involving the 737 Max. But he would not pledge his company’s support for stricter laws.

“We have to get the balance right,” Muilenburg said. “It’s very important we have strong government oversight, strong FAA oversight.”

Lawmakers have said they are weighing changes to aviation safety laws in the wake of the crashes. Investigators have focused in particular on a legal set up that allows Boeing and other manufacturers to take on much of the work of certifying that aircraft are safe.

A second day of hearings before the House Transportation and Infrastructure Committee, which has been investigating the crashes, is set for Wednesday.

According to his prepared remarks, committee chairman Rep. Peter A. DeFazio (D-Ore.) plans to say Boeing had information that some pilots would take far longer to respond to a new automated feature implicated in both crashes than the four seconds relied on by the company “and that if that happened, the results would be catastrophic, resulting in the loss of the aircraft.”

The evidence for the statement is not clear from the remarks released by DeFazio’s staff Tuesday and his office declined to provide details.

During Tuesday’s hearing, Sen. Richard Blumenthal (D-Conn.) said Boeing had misled his office after the crashes, blaming them on pilot error. In reality, Blumenthal said: “Those pilots never had a chance.”

Blumenthal asked Muilenburg to commit to supporting efforts to change the safety certification system, but Muilenburg committed only to participating in its efforts. He denied it was the company’s position to blame the pilots.

“We are responsible for our airplanes,” Muilenburg said.

Committee Chairman Roger Wicker (R-Miss.) trained early criticism on both Boeing and the Federal Aviation Administration. Wicker pointed to recently released correspondence between Boeing and the FAA, saying it reflected “a disturbing level of casualness and flippancy” that seemed to corroborate criticisms of an “inappropriately close relationship” between manufacturer and regulator.

In one of the emails, Boeing’s former chief 737 technical pilot, Mark Forkner, said he would be ­“jedi-mind tricking regulators into accepting the training that I got accepted by FAA etc.,” a reference to the company’s successful campaign to minimize training for pilots who would be flying the Max.

Pressed by Wicker on when Muilenburg learned of that email, the CEO said he had been informed of the details “just recently,” as they were being reported publicly.

“I don’t recall being briefed on the documents any time prior to that,” Muilenburg said. “The comments, the values, the approaches that are described in those emails, are counter to our values.”

Muilenburg said the company had made mistakes, and he expressed deep remorse. “As a husband and father, I am heartbroken by your losses,” he told survivors of those killed in Indonesia and in Ethi­o­pia under similar circumstances within five months. The family members, sitting three rows back from Muilenburg, at one point held up photographs of their lost husbands, wives and children.

Shortly after the Lion Air flight took off, the captain and first officer began to struggle with the controls, as the new automated feature on the Max received erroneous sensor data and repeatedly forced the nose down. The crash killed 189 people.

Information about the feature — the Maneuvering Characteristics Augmentation System (MCAS) — had been kept out of the Flight Crew Operating Manual on Boeing’s assumption that it would only rarely kick in.

“Delete MCAS,” Forkner wrote to an FAA official in 2017 as the plane’s five-year certification was nearing the finish line.

The deletion served Boeing’s commercial interest at the time, which was to minimize the regulations it had to follow and the amount of costly training required of its customers.

Less than five months after the Indonesian tragedy, an Ethiopian Airlines flight crashed in similar circumstances, killing another 157 people.

Soon after that crash regulators worldwide moved to ground the Max.

The crashes have been a major crisis for Boeing. The grounding of the Max, a more fuel efficient version of the popular 737, has hurt the company’s finances and stock price and shaken public confidence.

Sen. Tammy Duckworth (D-Ill.), a former Army helicopter pilot, challenged Muilenburg’s assertion that the development of MCAS followed industry standards. She said the feature was designed in such a way that it worked against pilots’ training to pull back on their controls when the nose of their plane dips.

“You’ve not been telling the committee the whole truth,” she said.

Muilenburg pushed back against criticism from senators about the safety certification process used for planes in the United States, which includes a convoluted structure involving both manufacturers and the FAA known as Organization Designation Authorization (ODA).

When asked by Sen. Jon Tester (D-Mont.) whether the certification process should revert to the FAA, Muilenburg emphasized the need for collaboration.

“We are open to improving it. But the idea that we can tap the deep technical expertise of our companies across the aerospace industry is a valuable part of the certification process,” Muilenburg said.

Tester said he remained unconvinced by the company’s pledges.

“Boeing has had an incredibly valuable name, but I’ve got to tell you, I would walk before I was to get on a 737 Max,” Tester said. “I would walk. There’s no way. The question becomes when issues like this happen, it costs your company huge. And so you shouldn’t be cutting corners, and I see corners being cut, and this committee has got to do something to stop that from happening.

Sen. Ted Cruz (R-Tex.) told Muilenburg his testimony was “ quite dismaying.”

Over a tense, 56-second stretch, Cruz read, word for word, the heart of an instant message exchange between Forkner and another technical pilot that raised concerns — in 2016 — about the performance of MCAS.

Muilenburg sat silent at the hearing table.

“Mr. Forkner, ‘So basically I lied to the regulators (unknowingly),’ ” Cruz read.

“Gustavsson: ‘It wasn’t a lie, no one told us that was the case.’ ”

Cruz continued, quoting Forkner saying MCAS was engaging “like crazy.”

“Forkner: ‘Granted, I suck at flying, but even this was egregious.”

Cruz stopped, then declared: “That exchange describes what happened in Lion Air and Ethiopian Air.”

He tried to pin down Muilenburg on what he knew about the exchange and when. Earlier in the hearing, Muilenberg said he had been “made aware” of the exchange before the Ethiopia crash but only “became familiar with the details” of it in the past few weeks.

“Mr. Muilenburg, how in the hell did nobody bring this to your attention in February” when Boeing provided it to the Justice Department. “How did you just read this a couple weeks ago?” Cruz asked.

“I was made aware of the existence of this kind of document, this issue, as part of that discovery process in the investigation, early in the year, as you pointed out. At that point, I counted on my counsel to handle that appropriately,” Muilenburg said.

On Monday, the chairmen of the House and Senate committees holding this week’s hearings both said they expect Congress to consider changing aviation safety laws. But exactly what such a change might look like remains unclear.

In the months since the Ethiopian crash, Boeing has been working on fixes to the automated feature, stopping it from turning on several times in a row and requiring it to read data from two sensors as a fail safe. The FAA has been reviewing that work as it determines when to allow the plane to fly again.

At the same time, investigators for the Justice Department, international aviation regulators and lawyers for the victims’ families have been examining how Boeing designed the Max and the FAA’s role in approving it as safe.

Investigations have found that the FAA received fragmented information about the automated feature, which meant it did not get close enough scrutiny.

After Muilenburg testified, the family members who attended said they were dissatisfied by his apology and what they saw as his failure to answer some of the Senators’ questions.

Pawel Konarski, whose wife and young son died on the Ethiopian Airlines flight, said the hearing left him angry. He said the second crash was preventable and had no idea of the danger his wife and son were in when they got on the plane.

“When they left me I thought we had procedures and regulations and laws and a lot of agencies and authorities that were looking over,” he said. “But I was wrong. I was wrong.”