Airliners manufactured by Boeing and Airbus have components made from titanium that was sold with fake documentation.

The Federal Aviation Administration (F.A.A.) revealed the problem after Boeing reported it to the agency when it was notified by parts supplier Spirit AeroSystems. Spirit AeroSystems, the same company that made the door on the 737 Max plane which suffered a door blowout on January 5, is at the center of this issue.

The falsified documents are being investigated by Spirit AeroSystems, which supplies fuselages for Boeing and wings for Airbus, as well as the F.A.A. The investigation began after a parts supplier found small holes in the material from corrosion. Spirit was testing the metal to determine if it was up to standard and structurally sound enough.

“This is about documents that have been falsified, forged, and counterfeited,” Spirit AeroSystems stated. “Once we realized the counterfeit titanium made its way into the supply chain, we immediately contained all suspected parts to determine the scope of the issues.”

The F.A.A. said in a statement that it “will investigate further the root cause of the document traceability issue and continues to monitor closely any new developments that could potentially lead to an unsafe condition in the fleet.” The agency is trying to determine the short- and long-term safety implications for planes made using the parts. It is unclear how many planes have parts made with the questionable material.

Boeing, in its statement, reported a voluntary disclosure to the F.A.A. regarding the procurement of material through a distributor who may have falsified or provided incorrect records. “Boeing issued a bulletin outlining ways suppliers should remain alert to the potential of falsified records,” the company added.

The European Union Aviation Safety Agency (EASA), which oversees Airbus, said it learned of the issue from authorities in Italy and began an investigation. So far, the agency said, it has not found indications of a safety problem. The problem was discovered after a parts supplier found small holes in the titanium from corrosion.

The Italians reported that they had purchased a batch of titanium alloys from Turkey and India due to their low cost. They kept the Chinese titanium alloys for their own use and sold the Indian titanium alloys to the Americans.

However, the batch from India was actually aluminum alloy, chosen for its lower cost. The Americans did not detect any issues during quality inspection, allegedly due to the use of forged reports.