The United States operated secret spy missions out of South Australia with its long-range Global Hawk surveillance drones, possibly over Afghanistan and off the North Korean coast.
The missions began shortly after the September 11, 2001, terror attacks and continued until at least 2006.
They were kept hidden after the US stamped on plans by former Liberal Defence Minister Robert Hill to make the flights public.
The South Australian Premier at the time, Labor's Mike Rann, was not told of the operations flown from Edinburgh Air Force Base near Adelaide, home of the RAAF's fleet of APC3 Orion long-range patrol aircraft.
The Global Hawk missions were uncovered by local aviation history enthusiasts and reported on ABC television's Foreign Correspondent programme. The Defence Department confirmed to the ABC that "rare" visits had occurred for "short replenishment purposes".
A Global Hawk made Australian headlines during the drone's only public visit in April 2001, after flying more than 13,200km from Edwards Air Force Base in California to become the first unmanned aerial vehicle (UAV) to cross the Pacific.
At the time of the Global Hawk's Adelaide flights, Australia was planning to buy up to seven sophisticated, long-range UAVs to operate with new Boeing P-8A Poseidon aircraft intended to replace the Orions in 2018.
The two options under consideration were the Global Hawk, made by Northrop Grumman, and the rival General Atomics Mariner, which underwent evaluation at Edinburgh in 2006.
The plans were deferred, although the RAAF operates leased Israeli Heron UAVs in Afghanistan and the army used smaller Shadow drones.
There are also long-term plans to fly UAVs such as the Global Hawk from Australia's remote Cocos Islands in the Indian Ocean.
South Australian operations by the big, A$200 million drones - whose wingspan is longer than a 747 jumbo jet's - were uncovered by members of Adelaide's West Beach Aviation Group.
The group monitors aircraft radio frequencies 20 hours a day to alert them to aircraft of interest, and they became aware of the Global Hawk's presence after "unusual chatter" and a strange call sign indicated the UAV was lining up to land 200 nautical miles away, when over Port Augusta in the Spencer Gulf, west of Adelaide.
The group's spokesman, Paul Daw, told Foreign Correspondent the Global Hawks began slipping into South Australia two months after the September 11 attacks.
"The reason we knew a Global Hawk was coming is we'd see a C141 Starlifter [transport aircraft] arrive up to a week earlier and unload a shipping container or two," he said.
"These [had equipment] to control the approach of Global Hawk."
Daw said the drones usually approached and left at night, although there were a few exceptions thathad enabled the group to photograph them.
The group recorded 10 missions to Adelaide, but Daw said there could have been others.
He said the flights were believed to be surveillance missions over Afghanistan.
The group monitored the flights until Australian military security officials insisted they stop. Their reports had been posted on an international website and published in the group's newsletter.
But Foreign Correspondent reported that in February 2006 an American journalist from the magazine Aviation Week and Space Technology was given access to a report on a single Global Hawk reconnaissance mission from RAAF Edinburgh to southern Japan and back again.
Officially, this was a demonstration flight for the Japanese, who were keen to acquire Global Hawk, the programme said.
But the visit occurred a week after North Korea conducted a series of missile tests and during a period when the US was intent on assessing North Korea's offensive military capabilities.
Matthew Aid, an American analyst specialising in US intelligence operations since 9/11, told Foreign Correspondent maintenance and refuelling stops at Edinburgh made sense onthe completion of missions or whenthe drones were in transit fromthe US to the Middle East and other locations.