Australia is helping the US investigate how parts for the F-35 stealth fighter program went missing after being mistakenly diverted to the wrong destination, Defense Minister Richard Marles has confirmed.

The incident occurred earlier this year, when a shipment of unserviceable F-35 components from Australia that was bound for the US was unexpectedly rerouted to Hong Kong. The parts, which were being transported by a third-party company on behalf of manufacturer Lockheed Martin, remain unaccounted for months later. Politico first reported the incident last week.

Marles said on Tuesday that Canberra was working with the US and Lockheed Martin to examine its role in the incident, stressing that the missing components were not sensitive.

Marles did not elaborate on why the components were considered non-sensitive and, when pressed by a journalist, said the question was best directed to the US and Lockheed Martin. Politico reported that the shipment included an F-35 canopy incorporating radar-resistant technology, although it remains unclear exactly which canopy components were involved.

The F-35 is a US-made fifth-generation stealth fighter operated by the US and its allies, with 12 countries currently flying the aircraft from bases on their own territory.

The Pentagon’s F-35 Joint Program Office has acknowledged a “shipment issue” involving unserviceable components to the news outlet and said it is working with US authorities and industry partners to recover the parts. The House Armed Services Committee is also examining the case, while Pentagon and State Department officials reportedly began briefing congressional staff on it in June.

The incident has highlighted potential vulnerabilities in the F-35’s sprawling global supply chain. Spare parts are routinely shipped between military bases, regional warehouses, and repair facilities, with Lockheed Martin overseeing much of the network on behalf of the Pentagon. Commercial carriers and other contractors are also used to transport components internationally.

F-35 parts have gone missing before. According to a US Government Accountability Office (GAO) report released in May 2023, one of the F-35 program’s prime contractors had recorded losses of more than 1 million spare parts worth over $85 million since May 2018, including components that were lost, damaged, or destroyed. The F-35 Joint Program Office had reviewed fewer than 2% of those cases. GAO also found that the military lacked its own comprehensive system for tracking the location, quantity, and cost of parts held in the contractor-managed global pool.

The inventory problems are part of broader difficulties that have dogged the F-35, the Pentagon’s largest weapons program. The aircraft has faced years of cost growth, maintenance and spare-parts shortages, upgrade delays, and persistent difficulties meeting Pentagon readiness targets.