Boeing CEO Dennis Muilenburg faced tough questioning from U.S. senators on Tuesday about two crashes of 737 Max jets that killed a total of 346 people and whether the company concealed information about a critical flight system from regulators.

"We have learned and are still learning from these accidents," Muilenburg said, according to comments prepared for his committee appearance. "We know we made mistakes and got some things wrong. We own that, and we are fixing them."

Muilenberg apologized directly to the families of victims to begin his testimony. Several of them were in the committee room, stating he was "heartbroken about your losses."

Muilenberg, in the first of two days of testimony on Capitol Hill, said the company is committed to strengthening its oversight processes and its communication between technical teams.

But Democrat Richard Blumenthal of Connecticut blasted the Boeing chief, took the company to task for initially pointing in the direction of pilot error as a significant factor, even though it has since been learned that most pilots did not know about the flight-control system called Maneuvering Characteristic Augmentation System (MCAS).

At Boeing's request, an explanation about it was excluded from pilot manuals.

"Those pilots never had a chance. These loved ones never had a chance," said Blumenthal. "They were in flying coffins as a result of Boeing deciding it was going to conceal MCAS from the pilot."

Several family members of victims who died in the two Max 737 crashes pose with pictures of their loved ones, including several Canadians, outside the Senate committee room. (Syliva Thomson/CBC)

Illinois Democrat Tammy Duckworth added that Boeing "set those pilots up for failure" by not telling them how the response to a nose-down command on the Max differed from previous 737s.

In his statement, Muilenburg said, "Our airline customers and their pilots have told us they don't believe we communicated enough about MCAS — and we've heard them."

Boeing is fixing the flight-control software and hopes to win Federal Aviation Administration (FAA) approval by year end to return the plane to flight early in 2020. The FAA is also coming under scrutiny for relying on Boeing employees to perform some certification tests and inspections. It's an approach the FAA has followed for many years.

Mississippi Republican Roger Wicker, the committee chair, criticized that relationship for its "coziness," pointing specifically to some since-discovered messages between Boeing's top technical pilot and FAA employees that he described as exhibiting "a disturbing level of casualness and flippancy."

That since-departed Boeing official spoke of "Jedi mind-tricking" regulators.

ICYMI: <a href="https://twitter.com/SenatorWicker?ref_src=twsrc%5Etfw">@SenatorWicker</a> “As chairman of this committee, I promise their loved ones that we are working to obtain a full answer as to how to prevent future tragedies.”<br><br>Click for the full opening statement from today’s hearing on aviation safety: <a href="https://t.co/iBLPfBusls">https://t.co/iBLPfBusls</a> <a href="https://t.co/JpLPvyXH4K">pic.twitter.com/JpLPvyXH4K</a> —@SenateCommerce

Wicker said it was imperative for the industry to ensure the interface between human operators and technologies is seamless going forward.

Congress is expected to consider changes to the way the FAA certifies new planes and its practice of deputizing employees of Boeing and other aircraft manufacturers to perform safety tests on key components.

Montana Democrat Jon Tester accused Boeing of cutting corners on safety.

"I would walk before I was to get on a 737 Max," Tester told Muilenburg. "When issues like this happen, it costs your company huge."

Boeing CEO Dennis Muilenberg faced heavy criticism during his testimony to a U.S. Senate committee over the crashes of two 737 Max jets that killed a total of 346 people. 2:42

Boeing CEO 'owes me a lot': Calgary woman

The Max was grounded worldwide after a March 10 crash involving Ethiopian Airlines flight 302, in which 157 were killed. The deceased included 18 Canadians, with relatives of some of those victims travelling to Washington to attend on Tuesday.

Gladys Kivia of Calgary, who lost her husband Derick Lwugi in the crash, said Muilenburg "owes me a lot."

Gladys Kivia of Calgary was among a group of Canadians who travelled to Washington, D.C., for the testimony. (Sylvia Thomson/CBC)

She faults the company for a lack of responsiveness to victims' families in the aftermath of the crash.

"No one ever called me to say, 'Gladys, I'm sorry,'" she said. "It's as if my husband's life did not matter."

In several lawsuits filed on behalf of Canadian victims of the Ethiopian Airlines crash, plaintiffs allege the pilots were in a tug-of-war with the plane's automated flight system, manually trying to climb while the computer caused the craft to dive repeatedly and ultimately crash.

Muilenberg's testimony comes exactly one year after a Lion Air Boeing 737 Max 8 jet crashed off the coast of Indonesia, killing 189 people.

Relatives of victims scattered flowers Tuesday on waters where the aircraft went down.

Edward Sirait, Lion Air's CEO, expressed condolences to relatives of those who died and said the company would follow recommendations from a report released last week by Indonesian transport officials. The report said faulty design by Boeing, inadequate training for the pilots and lapses in maintenance doomed Lion Air flight 610.

Questioned about response to 1st crash

Back in Washington, Republican Sen. Ron Johnson of Wisconsin asked why Boeing didn't ground the planes immediately after the first accident, when it knew that MCAS was involved.

"We have asked that question over and over," Muilenburg said. "If we knew everything back then that we know now, we would have made a different decision."

Boeing will also be grilled on Wednesday by lawmakers in the House of Representatives.

If we knew everything back then that we know now, we would have made a different decision - Boeing CEO Dennis Muilenburg

Peter DeFazio, Democratic chair of the House Transportation Committee, said he will ask why Boeing didn't tell the FAA about changes during development of the Max that made MCAS more powerful.

The Oregon Democrat suggested that Boeing concealed the true power of MCAS to discourage regulators from examining the system more closely.

"There are numerous regulators looking at this. It isn't just going to be the FAA. This will be the most thoroughly scrutinized fix in the history of the aviation industry."

Speaking briefly to reporters before entering the room, Muilenberg refused to speculate on his future with the company, which is headquartered in Chicago but employs most of its U.S. workers at its Seattle-area campus.

"My focus is on the job at hand," he said. "We're focused on safety, and we're going to do everything we can to ensure safe flights going forward."

Muilenburg, who is expected to meet with some of the family members Wednesday, was stripped of his title as chairman of the Boeing board earlier this month. The most senior executive dismissed so far was the head of Boeing's commercial airplanes division, Kevin McAllister.

WATCH | Families of Lion Air and Ethiopian Airlines victims speak ahead of Tuesday's hearing: