Daniel Edmund Duggan, an Australian citizen, "provided training to PRC [People's Republic of China] military pilots" at a South Africa-based flight academy on at least three occasions between 2010 and 2012, according to the 2017 indictment unsealed by a court in Washington last week.

Duggan was arrested in Australia in October, the same week Britain and Australia issued unusually candid warnings about China's attempts to recruit retired military pilots.

The training involved "instruction on the tactics, techniques, and procedures associated with launching aircraft from, and landing aircraft on, a naval aircraft carrier," the indictment said.

Neither Duggan nor his co-conspirators had applied for a license to provide defence services to foreign nationals, it said.

The former US Marine had acted with several unidentified co-conspirators, including a Chinese national, a British national, and a South African national, it added.

According to the indictment, Duggan faces two counts of violating the arms export control act and international arms trafficking regulations, one charge of conspiracy to launder money, and one count of conspiracy.

He has been detained under Australia's Extradition Act, pending an official request from the US government.

His lawyer said last month Duggan had been classified as an "extreme high-risk restricted inmate" inside a maximum-security facility in Sydney and had been denied access to writing materials and medical treatment.

Duggan lived and worked in China for about five years before his arrest, corporate records showed, although the details of his alleged offences have been sealed by the US government.

He moved to Australia after leaving the US Marines, running the Top Gun adventure flight company from the southern island of Tasmania.

Top Gun's website said Duggan spent more than a decade flying in the US Marine Corps, reaching the rank of major and working as a tactical flight instructor.