Current and former Boeing employees delivered stark warnings at two U.S. Senate hearings on Wednesday over safety culture and manufacturing quality at the planemaker.

They've been under scrutiny since the door plug panel blew off an Alaska Airlines flight in January.

Testimony at the U.S. senate permanent subcommittee on investigations raised questions about missing records surrounding the panel.

Former Boeing manager Ed Pierson said an internal whistleblower sent him records about the plug, that he had turned over to the FBI.

"The manufacturing conditions that led to the two 737 Max disasters also led to the Alaskan accident blowout accident, and these conditions continue..." // "The world is shocked to learn about Boeing's current production quality issues. I'm not surprised because nothing changed after the two crashes."

Boeing has said it believed that required documents detailing the removal of the door plug were never created.

The hearings come amid a management shakeup at Boeing.

U.S. regulators have put curbs on production and in March, its deliveries fell by half.

Also under the spotlight on Wednesday: two of Boeing's widebody jets.

SALEHPOUR: "I have serious concerns about the safety of the 787 and 777 aircraft, and I'm willing to take on professional risk to talk about them."

Quality engineer Sam Salehpour has claimed Boeing failed to adequately shim -- or use a thin piece of material to fill tiny gaps -- an omission that could cause premature fatigue failure over time in some areas of the Boeing 787 Dreamliner.

"Boeing had problems pushing pieces together with excessive force to make them appear that the gaps don't exist, even though they exist."

Salehpour has said he was transferred off the 787 program over his questions.

Boeing has challenged Salehpour's claims against the 787 and 777, which fly internationally.

On Monday, it said it had not found fatigue cracks on nearly 700 Dreamliner jets in service that have gone through heavy maintenance.

In a statement on Wednesday, Boeing defended the planes' safety; Noting that the global 787 fleet has safely transported more than 850 million passengers, and the 777 -- 3.9 billion travelers.

The FAA said in a statement that every aircraft flying complies with the regulator's airworthiness directives.