The US Federal Aviation Administration (FAA) has launched an investigation into titanium used in Airbus and Boeing aircraft after a key but embattled supplier, Spirit AeroSystems, alerted it about counterfeit documentation originating from a Chinese supplier of the metal, the New York Times reported.

"Boeing reported a voluntary disclosure to the FAA regarding 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 FAA said in a statement.

Spirit AeroSystems initially spotted "small holes from corrosion" in the titanium parts and launched an investigation to verify whether, despite their fake documentation and unknown origin, the titanium alloys meet the structural standards for aviation-grade materiel. Spirit uses titanium in B737 MAX, B787, and A220 parts machined at its factories.

Both manufacturers said tests have so far not shown any issues that would affect the airworthiness of their aircraft. Boeing and Spirit AeroSystems said they are proactively removing any potentially affected parts from aircraft in assembly.

It is currently unclear how many aircraft are potentially affected and whether the issue would force operators to perform unscheduled maintenance to replace any flagged parts. However, anonymous internal sources told the New York Times that the issue affects aircraft built between 2019 and 2023.

According to the reports, Turkish Aerospace Industries acquired the counterfeit titanium in 2019 from an unnamed Chinese supplier which had forged certificates of conformity for the metal, pretending it was sourced from a well-known supplier, Baoji Titanium Industry, which in turn confirmed it was not involved in the transactions. The titanium was eventually sold to Spirit via other suppliers.