“More than 1,000 tests have been completed to confirm the mechanical and metallurgical properties of the affected material to ensure continued airworthiness,” Buccino said.

Airbus identified its A220 model as being affected; Boeing declined to say what planes were involved in the issue but said it affected only a small number of parts on any aircraft.

The problem with the titanium, which was first reported by the New York Times, highlights the heightened concern about fake or improperly documented parts entering the aviation supply chain in recent years and the growing pressure on the supply of titanium. Aircraft manufacturers rely on a sprawling network of suppliers, making it difficult to oversee quality. Several manufacturers launched a task force in February to try to better address the issue.

The FAA said in a statement that Boeing disclosed the issue to regulators voluntarily and issued a bulletin to suppliers, reminding them to be alert to the potential of falsified records. The agency said it was investigating the scope of the problem.

The European Union Aviation Safety Agency, 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 agency 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.”

While manufacturers said there were no immediate safety concerns, the disclosure of the questionable titanium was made as Boeing remains under close scrutiny by the FAA and lawmakers. Reviews continue over the midair door panel blowout on an Alaska Airlines 737 Max in January and accounts from whistleblowers alleging improper manufacturing processes. Boeing chief executive Dave Calhoun is scheduled to testify in front of a Senate panel investigating the issues next week.

The Times reported that an investigation into the titanium came after a supplier found small holes in the metal linked to corrosion. The metal entered the supply chain from China via Italian and Turkish companies, according to a person briefed on the situation who spoke on the condition of anonymity due to the ongoing investigation.

Titanium is light but strong, making it useful in aircraft. But as demand has grown in recent years and fallout from the war in Ukraine has constrained Russian supplies, experts say aviation suppliers have increasingly turned to Chinese sources for the metal, where the early stages of production are highly concentrated.

Those Chinese sources can be difficult to trace. That poses a problem because titanium is highly reactive during production, meaning metal intended for use in planes has to be made under highly controlled conditions to avoid contamination that can affect its strength and corrosion resistance, according to Taso Arima, the founder of titanium firm IperionX.

“We’ve got a broken supply chain,” said Arima, whose company is starting to produce the metal in the United States. “Being able to trace it is very difficult.”

Boeing said the titanium was linked to shipments involving a small group of suppliers. Tests of the metal have indicated that the metal was the right kind of titanium for use in aircraft, Boeing said.

“We are removing any affected parts on airplanes prior to delivery,” Boeing said in a statement. “Our analysis shows the in-service fleet can continue to fly safely.”

Airbus said that the airworthiness of its A220 model of single-aisle jets “remains intact” and that “the safety and quality of our aircraft are our most important priorities.”

As the aviation supply chain has grown more sprawling and complex, moving farther away from where the final manufacturing occurs, there has been growing concern in the industry and among regulators about how to ensure that the parts companies are receiving meet standards.

Last year, CFM International, an engine manufacturer, accused one of its suppliers, AOG Technics, of selling it thousands of engine parts with forged documents. In September, the FAA issued a formal notification over a part supplied by AOG Technics without the agency’s production approval. Britain’s Serious Fraud Office has launched a criminal investigation into the matter.

A subsequent review found that fewer than 1 percent of CFM engines used in older-generation Boeing 737 and Airbus A320 aircraft were affected, but the incident raised alarms in the industry. It led major manufacturers and U.S. airlines, including American and United, to form a supply chain integrity coalition. AOG Technics did not respond to a request for comment Friday.

The group, formed in February, is co-chaired by Robert Sumwalt, the former chair of the National Transportation Safety Board, and John D. Porcari, a former U.S. deputy secretary of transportation. As part of its work, it launched a 90-day review aimed at finding ways to strengthen existing supply chains, work that will be used to develop recommendations to block unapproved parts.

Porcari outlined some of the coalition’s work during a joint aviation safety conference sponsored by American and European Union regulators in Washington, D.C., this week. He said allegations against AOG Technics are not isolated incidents. He added that that coalition sees several areas — documentation, authentication and supplier standards and oversight — as key to its efforts.

“I want to underscore the pace and intensity of this work,” Porcari told conference attendees. “We’re trying to accomplish this very quickly. This is a unique pop-up potential safety issue and we’ve tried to move quickly in addressing it.”