A group of aviation historians detected at least 10 take-offs or landings of the $200 million RQ-4 Global Hawks in Edinburgh from 2001 to 2006. 
The U.S. Air Force (USAF) operates a fleet of 23 Global Hawks from a headquarters at Beale Air Base in California. The USAF also has a facility at Grand Forks, North Dakota, and forward operating bases at Al Dhafra in the United Arab Emirates, Sigonella U.S. Naval Air Station on Sicily and Andersen Air Force Base on Guam.
Aviation historians from the West Beach Aviation Group (WBAG) monitored aircraft radio frequencies and photographed the drones.
"Because of the type of call-sign and flight path used by the pilot, we knew it was Global Hawk coming in," WBAG spokesman Paul Daw told The Australian.
Australian defense officials demanded that they not publish any photos or information about the secret missions. WBAG members argued that there are no restrictions on photographing or monitoring U.S. aircraft in Australian skies and ended up publishing RQ-4 movements in their limited-circulation newsletter.
But most of the Australian public never found out as the USAF demanded that all Global Hawk operations remain 'codeword' top secret, or above top secret.
"Sometimes a Global Hawk would go out [from RAAF Edinburgh] on two or three flights. The aircraft would climb to 60,000 feet," Daw told ABC. "Who knows where they went ... they had enough fuel for 30 to 35 hours, and they'd return."
Global Hawk missions over the coastline of North Korea have been based out of Guam since 2010, and intelligence analyst Matthew Aid told ABC that "a forward operation location at Edinburgh would have been a perfect place" before 2010