The search in November was part of an investigation into Western military pilots training China's military at a time of growing tension between China and the United States and its allies.

Britain and Australia have announced crackdowns on former military pilots working to train Chinese fliers, and Britain vowed to change its national security law to stop them working for intermediaries including a South African flying school, which was alleged to be helping China's People's Liberation Army (PLA) recruit pilots.

Keith Hartley, chief operating officer of the Test Flying Academy of South Africa (TFASA), has not been charged.

He challenged the validity of the search warrant in Australia's Federal Court, questioning its wording and seeking the return of seized material.

The court rejected his application on April 28 and released its judgment, which sheds new light on the investigation into the South African flying school, which has a partnership with China's state-owned Aviation Industry Corporation of China (AVIC) to train Chinese pilots in South Africa, and had employed several Western pilots with military backgrounds.

Federal police searched Hartley's home on suspicion he had broken the law by providing military style training directed or funded by China between 2018 and 2022, the Federal Court heard.

The search warrant sought evidence to support an Australian police investigation into Hartley, who was suspected of organising or facilitating the training delivered by the flight school "to PLA pilots in regard to military aircraft platforms and military doctrine, tactics and strategy".

Hartley's lawyer, Dennis Miralis, told Reuters he was reviewing the court decision and seeking specialist legal advice on whether to appeal.

"Keith Hartley and TFASA deny any criminal wrongdoing in this matter," he said in a statement.

The judgement shows police had searched for documents and digital records including emails and encrypted messages relating to TFASA, the PLA, four models of PLA fighter jets and fighter training aircraft including the J-16 strike fighter and J-11 fighter, AVIC and two individuals whose names were redacted.

Police also searched for references to Australia's Five Eyes intelligence partners New Zealand, Canada, United States and Britain, as well as NATO and Australia's air force, the judgement shows.

In her judgement, Justice Wendy Abraham wrote that the nature of the alleged offence would have been clear to Hartley when he read the warrant, and police didn't need to provide details of how the PLA were alleged to have directed or funded the training.

"The applicant has not established that the warrant is invalid. It states conduct capable of constituting an offence, and it does so with a reasonable degree of precision," she wrote.

(Reporting by Kirsty Needham; Editing by Robert Birsel)

By Kirsty Needham