Boeing CEO Dave Calhoun will likely face tough questions Tuesday when a Senate panel grills the executive on safety problems, manufacturing missteps and alleged efforts to intimidate whistleblowers.

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.

"Five years ago, Boeing made a promise to overhaul its safety practices and culture. That promise proved empty, and the American people deserve an explanation," Democratic Senator Richard Blumenthal said earlier this month.

"Years of putting profits ahead of safety, stock price ahead of quality, and production speed ahead of responsibility has brought Boeing to this moment of reckoning, and its hollow promises can no longer stand."

The whistleblower allegations surrounding the 787 and 777 are only one of the myriad issues facing Boeing that could come up on Tuesday.

The company is also implementing safety upgrades under the tight supervision of the Federal Aviation Administration after a fuselage panel on a 737 MAX blew out mid-flight in January, necessitating an emergency landing and leading to a brief grounding of some MAX planes.

The Department of Justice meanwhile concluded in May that Boeing could be prosecuted for violating a criminal settlement following two fatal 737 MAX crashes in 2018 and 2019, off Indonesia and in Ethiopia. 

Next steps around a decision on whether to prosecute will come next month.

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 reiterated those points, emphasizing that the company has strict policies prohibiting retaliation against employees who report problems. 

"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."

Whistleblower alleges safety issues

At the April 17 hearing, witnesses painted a disturbing picture of a company that blew off 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.

Salehpour also testified that he was blackballed by company higher-ups and feared for his personal well-being after raising concerns about safety.

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.

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."