Airmen’s favorite F-35 stealth fighter jets are set to be grounded after an investigation showed there was illegally procured Chinese alloy in the component.

The Pentagon halted Lockheed Martin Corp’s new deliveries of the upgraded F-35 after they discovered the alloy used in the magnet for pumps was made in China. It is not confirmed whether this is affected by the current state of US-China relations, but the Defence Department Spokesman Russell Goemaere said they are checking if the alloy meets procurement regulations.

The F-35 programme office “temporarily paused the acceptance of new F-35 aircraft to ensure the F-35 programme’s compliance…pertaining to specialty metals,” Goemaere’s email notes.

However, since this material was only added in the new version of the F-35, the previous deliveries are not affected by the said compliance check. Furthermore, Goemaere added that the F-35s that were already delivered did not have magnets that transmit “information or harm the integrity of the aircraft and there are no performance, quality, safety or security risks associated with this issue.”