In a room crowded with crash victims' families, Boeing's chief executive faced a grilling by senators.
Dave Calhoun appeared before Congress for the first time since a door plug blew off a 737 Max 9 in January.
Turning and facing relatives of two crashes of Boeing 737 Max 8's in 2018 and 2019, Calhoun apologized.
"I apologize for the grief that we have caused," he said.
In the hearing, Calhoun took blame for the two crashes, saying that the design failures in the MCAS system and Boeing were at fault for the deadly crashes that killed 346 people.
Sen. Richard Blumenthal of Connecticut began the hearing, calling this a "moment of reckoning" and saying that the hearing today was about a company that "lost its way."
"We learned those tragedies were caused by intentional decisions to put production speed over safety and profits," said Blumenthal.
Calhoun defended the work Boeing has done to fix the engineering flaws as well as the work underway to make sure the manufacturing failures that led to the Jan. 5 door plug accident do not happen again.
"Our culture is far from perfect, but we are taking action and we are making progress. We understand the gravity and we're committed to moving forward with transparency and accountability," said Calhoun.
Some of the most intensive questioning came from Missouri Sen. Josh Hawley, asking Calhoun why he deserves his salary of $32.8 million.
"You're focused on exactly what you were hired to do, which is that you're cutting corners. You are eliminating safety procedures. You are sticking it to your employees. You are cutting back jobs because you're trying to squeeze every piece of profit you can out of this company," said Hawley.
Related story: Boeing reveals sweeping plan to improve quality control, culture
Hours earlier, the Senate released a report containing allegations from a whistleblower who feared Boeing was using unapproved parts and hid it from government inspectors.
The whistleblower, Sam Mohawk, was a quality assurance investigator at the 737 plant in Renton, Washington. Mohawk alleges that Boeing used parts that were either defective or parts that did not have proper documents in planes and then hid evidence of those decisions from the FAA.
Mohawk said in the report that his supervisors retaliated against him for coming out with that information.
In a statement sent to Scripps News, Boeing said: "We received this document late Monday evening and are reviewing the claims. We continuously encourage employees to report all concerns as our priority is to ensure the safety of our airplanes and the flying public."
In the hearing, Calhoun admitted retaliation against whistleblowers has happened and that some people were fired or punished because of it.
The Justice Department is still considering whether to prosecute Boeing for violating terms of a settlement in the crashes in Indonesia and Ethiopia.
Before the hearing, families of crash victims addressed reporters.
"To me justice is for them to be held accountable and be criminally charged and to face us in trial. Give us our day in trial," said Clariss Moore, whose daughter was killed in the 2019 crash in Ethiopia.
Prosecutors have until July 7 to decide the next step.
