United States lawmakers will press Boeing CEO on day two of testimony

Boeing Co Chief Executive Dennis Muilenburg faces a second day of questions Wednesday from US lawmakers on its now grounded 737 MAX after sharp criticism at a Senate hearing Tuesday.

US Representative Peter DeFazio, who heads the House Transportation and Infrastructure Committee, which will hear from Muilenburg on Wednesday, said in a written statement that the committee's lengthy investigation into the MAX has turned up significant questions about Boeing's decision-making.

"Something went drastically wrong, a total of 346 people died, and we have a duty to fix it," DeFazio will say in his opening statement.

DeFazio said the panel is aware of "at least one case where a Boeing manager implored the then-vice president and general manager of the 737 programme to shut down the 737 MAX production line because of safety concerns." Boeing did not comment Tuesday on the allegation.

Muilenburg told reporters on Wednesday he believes the allegation was in response to concerns about a change in the increase of the production rate. He said Boeing was aware of those concerns and had acknowledged them.

Muilenburg said that he had met with some family members of the victims before Wednesday's hearing. "It was tough to hear," he said, adding the company was making "the fixes we need to make."

The Boeing CEO on Tuesday acknowledged errors in failing to give pilots more information on a key safety system known as MCAS before the crashes, as well as for taking months to disclose that it had made optional an alarm that alerts pilots to a mismatch of flight data on the 737 MAX.

"We've made mistakes and we got some things wrong. We're improving and we're learning," he said.

The hearing, the highest-profile congressional scrutiny of commercial aviation safety in years, heaps pressure on a newly rejigged Boeing senior management team fighting to repair trust with airline customers and passengers shaken by an eight-month safety ban on its 737 MAX following the crashes.

"You have told me half-truths over and over again," Senator Tammy Duckworth told Muilenburg, questioning why the manufacturer did not disclose more details about MCAS's lack of safeguards. On Wednesday, Muilenburg said he would work to ensure she got the information she was seeking.

Taking turns to grill Muilenburg during his first appearance at a hearing on Capitol Hill in the year since the first crash in Indonesia, senators also expressed dismay that 2016 instant messages discussing erratic behaviour of simulator software - a replica of the system aboard the jetliner - did not prompt an immediate reaction from the company.

For months, Boeing had largely failed to acknowledge blame, instead vowing to make a "safe plane safer." Tuesday's hearing represents Boeing's broadest acceptance of responsibility that it made mistakes, but Muilenburg stopped short of what some lawmakers and family members had sought.

Family members were seated just three rows behind Muilenburg during his testimony and were invited at one point to stand and show large photos of their loved ones.

Nadia Milleron, whose daughter was killed in the Ethiopian Airlines crash in March, said Muilenburg and the board should resign for failing to do more to prevent the crashes.

As Muilenburg departed the hearing, she implored him to look at the victims' families when he apologized. He turned to her and said: "I'm sorry."