Boeing CEO Dave Calhoun is expected to apologize to families of crash victims on Tuesday as he faces a Senate grilling following accusations that the plane maker put profits over safety.

The hearing, an examination of "Boeing's Broken Safety Culture," follows an April session of the Senate Permanent Subcommittee on Investigations featuring a Boeing engineer who testified that he was punished for raising safety questions about the top-selling 787 Dreamliner and 777.

Calhoun's appearance will mark his first testimony before a congressional panel since an alarming mid-flight incident in January on a 737 MAX plunged the company back into crisis mode. US investigators are still probing the incident with the Alaska Airlines plane, which made an emergency landing after a fuselage panel blew out.

On Tuesday morning, the Senate committee detailed additional complaints from Boeing workers, including an official filing from a whistleblower who worried that Boeing's lax policies on the use of damaged or inadequate parts could "lead to a catastrophic event," according to a subcommittee memo.

Democratic Senator Richard Blumenthal, who will chair the session, said the litany of complaints from workers showed a culture "where those who speak up are silenced and sidelined while blame is pushed down to the factory floor," according to remarks distributed ahead of the hearing.

Calhoun was "brought in turn this company around," Blumenthal said. "But instead of asking what has caused Boeing's safety culture to erode, you and your colleagues in the C-suite have deflected blame, looked the other way, and catered to your shareholders instead."

Calhoun has previously apologized for the Alaska Airlines incident and announced production halts and other steps to improve safety and quality assurance.

In Calhoun's opening statement, released by Boeing ahead of the hearing, the CEO emphasized the company's anti-retaliation policies and said the company was determined to right the course.

"Our culture is far from perfect, but we are taking action and making progress," Calhoun said. "We understand the gravity, and we are committed to moving forward with transparency and accountability, while elevating employee engagement."

- New whistleblower -

At the April 17 hearing, witnesses painted a disturbing picture of a company that dismissed safety questions and sidelined critics as it chased faster production and bigger profits.

The star witness was engineer Sam Salehpour, who went public with allegations that, because of flawed manufacturing processes, the Dreamliner could suffer from premature fatigue, resulting in a potentially catastrophic accident because of excessively large gaps in the plane's assembly.

Boeing has pointed to extensive testing that it says proves the 787 is safe.

In connection with the probe, Blumenthal and Senator Ron Johnson, a Republican, sent a letter to Calhoun seeking records that would shed light on Salehpour's allegations about the 787 and 777, as well as records relating to Boeing's whistleblower policies and protocols.

The same two senators also sent a letter to FAA Administrator Michael Whitaker related to the allegations, as well as other ongoing Boeing-related matters, such as a six-week FAA audit of the company following the Alaska Airlines incident.

The Senate panel on Tuesday released details on additional workers who have come forward with problems.

This includes a new whistleblower, Sam Mohawk, who said that Boeing ordered improperly stored parts to be hidden from federal aviation inspectors, who would have demanded Boeing increase storage capacity and hire additional staff, raising costs.

Joining the hearing will be family members who lost relatives in the 2018 and 2019 MAX crashes, which together claimed 346 lives.

"I flew from England to Washington, DC, to hear in-person what the Boeing CEO has to say to the Senate and to the world about any safety improvements made at that corporation," said Zipporah Kuria, who lost her father in the 2019 crash.

"I also continue to press the US government to hold Boeing and its corporate executives criminally responsible for the deaths of 346 people. We will not rest until we see justice."

Calhoun, who will be accompanied at the hearing by Boeing Chief Engineer Howard McKenzie, apologized to the MAX families in his written remarks, saying "we are deeply sorry for your losses."