One year to the day since Lion Air Flight 610 plunged into the Java Sea, killing all 189 people aboard, Boeing CEO Dennis Muilenburg testified before Congress as to how the fatal accident happened and what his company is doing to regain public confidence.

The Indonesian crash was the first of two fatal accidents that killed a total of 346 passengers and crew and led to a worldwide grounding of the company's best-selling plane, as well as a ripple effect across the globe as airlines canceled thousands of flights and lost millions of dollars in revenue.

Muilenburg will answer questions from the Senate Committee on Commerce, Science and Transportation on the design of the plane, a 737 Max jet, the lack of training for pilots, and how the planes came to be approved and certified by regulators. Lawmakers are also expected to ask the CEO why he remains at the head of the embattled company.

In a brief question-and-answer session with reporters before the hearing, a contrite Muilenburg expressed "deepest sympathies" for the families of those who died, saying, "We learned a lot as a company. We're humbled. It has only amplified our focus on safety going forward."

When asked if he was feeling pressure to resign, Muilenburg said his focus remains on the job at hand. "Those aren’t discussions I’m involved in," he said. "We have important work to do for the world. Safety is at the very forefront of that."

Boeing's board stripped Muilenburg of his chairmanship earlier in October and last week replaced the head of the company's commercial plane division.

The aircraft maker reported its worst-ever quarterly loss in July this year, and has set aside $4.9 billion to compensate airlines for the grounding of hundreds of planes. The company's third-quarter profits were down by more than 50 percent.