As the Federal Aviation Administration continues to scrutinize one of the country's leading aircraft manufacturers, Sen. Chuck Grassley is announcing a new probe into aerospace giant Boeing and the FAA itself due to concerns of safety hazards and lax oversight.

"Boeing enjoys billions of taxpayer dollars every year, and thousands of Americans rely on Boeing aircrafts to get from Point A to B every day," the Iowa Republican told Fox News Digital. "By cutting corners or turning a blind eye to glaring problems, Boeing puts passengers’ safety at serious risk."

Grassley pointed to what he called a "history of aircraft disasters" involving Boeing jets going back to the explosion of TWA Flight 800 in 1996 and including Alaska Airlines Flight 1282, where a Boeing 737 Max craft lost a door panel at 16,000 feet in January. Eight people suffered minor injuries.

"Had this happened at cruising altitude the results might have been catastrophic," Grassley wrote in a letter to outgoing Boeing CEO David Calhoun.

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In letters to Calhoun and the FAA, Grassley demanded an explanation for what went wrong and what's being done to stop it from happening again.

"Boeing is given great responsibility to build the planes that Americans rely on every day, and the FAA is entrusted to ensure they do it safely," he wrote. "Boeing’s track record, as well as recent reports, demonstrate that aircraft safety has not been the paramount concern and the FAA has provided insufficient oversight to ensure that it is."

Grassley's office described Boeing's quality control and oversight practices as "questionable, at best" and called on the FAA to step up its oversight.

"The FAA ought to do the job taxpayers are paying the agency to do by keeping the pressure up on its scrutiny of Boeing and holding the company accountable for aviation safety failures that employees, as well as bipartisan lawmakers including myself, are bringing to light," he said.

The FAA declined to comment and said it would be responding directly to the senator.

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Grassley also condemned allegations of whistleblower retaliation, referencing the recent suicide of John Barnett, who claimed that a Boeing plant in South Carolina was using substandard parts and lost track of defective components.

His death in March was ruled a suicide. It came as he was in the middle of depositions as part of his retaliation lawsuit against Boeing, and his lawyers argued that the company is responsible for his death.

"Mr. Barnett’s last words make clear that while Boeing may not have pulled the trigger, the company is responsible for his death," Barnett's lawyers, Robert Turkewitz and Brian Knowles, said in a joint statement after police released their client's suicide note.

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In it, he wrote in part that he couldn't "do this any longer" and apologized to his loved ones.

"Bury me face down so Boeing and their lying a-- leaders can kiss my a--," he added.

Investigators determined that Barnett suffered from PTSD, anxiety and panic attacks, conditions that his lawyers blamed on Boeing.

Last week, the New York Times revealed that the FAA is investigating how titanium of unverified origin, possibly counterfeit, made its way into a Boeing contractor's supply line after its sellers hid its provenance with forged documentation.

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Boeing uncovered the issue and alerted federal authorities and its suppliers, according to the FAA. The issue also reportedly impacted Boeing's main competitor, Airbus.

"Boeing reported a voluntary disclosure to the FAA regarding procurement of material through a distributor who may have falsified or provided incorrect records," the FAA said in a statement. "Boeing issued a bulletin outlining ways suppliers should remain alert to the potential of falsified records."

The FAA said it was looking into the "scope and impact" of the issue.

Read Sen. Grassley's letter to Boeing CEO Dave Calhoun. App users: click here.

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The contractor, Spirit AeroSystems, did not immediately respond to a request for comment. However, a spokesperson told the Times that the company had "contained all suspected parts" that used the questionable alloy.

Grassley also pointed to what he called Boeing's "history of aircraft disasters," including two deadly crashes in 2018 and 2019 and the explosion of TWA Flight 800 in 1996, which killed a combined 573 people.

Boeing did not immediately respond to a request for comment.

Boeing previously said that some wear-and-tear issues are the responsibility of airlines, which maintain their own fleets, and not manufacturing defects. 

Last week, the company told FOX Business that it was investigating some fasteners on a batch of undelivered 787 Dreamliner jets that may have been installed incorrectly.