Washington: The Pentagon and Australian defence authorities are investigating how two unserviceable components from an Australian F 35 fighter aircraft were diverted to Hong Kong in late May while being transported to the United States for inspection, possible repair or disposal.

The shipment reportedly contained a cockpit canopy and a weapons bay door. UPS was transporting the components on behalf of F 35 manufacturer Lockheed Martin when the cargo was redirected through South Korea to Hong Kong.

The reason for the diversion has not been publicly established.

The Pentagon’s F35 Joint Program Office confirmed a shipment problem involving unserviceable components. It said American authorities and industry partners were working to retrieve the parts, investigate the incident and prevent a recurrence.

Reports said the canopy and door contained radar absorbing material. Such material helps reduce the aircraft’s radar signature, making it more difficult to detect. The F 35 is a fifth generation combat aircraft designed around stealth, advanced sensors and networked operations.

Australian Defence Minister Richard Marles said Canberra was examining its involvement but had been advised that the missing components were not classified as sensitive. Lockheed Martin described the parts as unserviceable and presenting a low risk of exploitation.

Media reports said Chinese authorities had taken possession of the shipment. However, no public evidence has established that China examined, tested or copied the components.

The Pentagon has not disclosed whether the parts remain intact, where they are currently being held or when they may be returned.