SEATTLE (AP) -- The Federal Aviation Administration said Monday it has opened an investigation into Boeing after the beleaguered company reported that workers at a South Carolina plant falsified inspection records on certain 787 planes. Boeing said its engineers have determined that misconduct did not create "an immediate safety of flight issue."

In an email to Boeing's South Carolina employees on April 29, Scott Stocker, who leads the 787 program, said a worker observed an "irregularity" in a required test of the wing-to-body join and reported it to his manager.

"After receiving the report, we quickly reviewed the matter and learned that several people had been violating Company policies by not performing a required test, but recording the work as having been completed," Stocker wrote.

Boeing notified the FAA and is taking "swift and serious corrective action with multiple teammates," Stocker said.

No planes have been taken out of service, but having to perform the test out of order on planes will slow the delivery of jets still being built at the final assembly plant in North Charleston, South Carolina.

Boeing must also create a plan to address planes that are already flying, the FAA said.

The 787 is a two-aisle plane that debuted in 2011 and is used mostly for long international flights.

"The company voluntarily informed us in April that it may not have completed required inspections to confirm adequate bonding and grounding where the wings join the fuselage on certain 787 Dreamliner airplanes," the agency said in a written statement. "The FAA is investigating whether Boeing completed the inspections and whether company employees may have falsified aircraft records."

The company has been under intense pressure since a door plug blew out of a Boeing 737 Max during an Alaska Airlines flight in January, leaving a gaping hole in the plane. The accident halted progress that Boeing seemed to be making while recovering from two deadly crashes of Max jets in 2018 and 2019.

Those crashes in Indonesia and Ethiopia, which killed 346 people, are back in the spotlight, too. The families of some of the victims have pushed the Justice Department to revive a criminal fraud charge against the company by determining that Boeing's continued lapses violated the terms of a 2021 deferred prosecution agreement.

In April, a Boeing whistleblower, Sam Salehpour, testified at a congressional hearing that the company had taken manufacturing shortcuts to turn out 787s as quickly as possible; his allegations were not directly related to those the company disclosed to the FAA last month. The company rejected Salehpour's claims.

In his email, Stocker praised the worker who came forward to report what he saw: "I wanted to personally thank and commend that teammate for doing the right thing. It's critical that every one of us speak up when we see something that may not look right, or that needs attention."