Australian Prime Minister Tony Abbott announced April 10 the purchase of the two strategic airlifters at RAAF Base Amberley, southwest of Brisbane. The two aircraft will bring the total number of C-17s in Australian ownership to eight.
Minister for Defence Kevin Andrews said that AUS $1 billion (US $777 million) would be spent on acquiring the two aircraft, including $300 million of infrastructure works at Amberley.
"Australia has worked closely with the United States Air Force to acquire the first aircraft within six months of the initial order and the second aircraft within 10 months of the delivery of the first," the minister said.
"This will mean that the ADF will gain additional operating capability within a short timeframe."
Last October, former Australian Defence Minister David Johnston forecast the acquisition of the two additional aircraft and said the Australian government was also requesting pricing and availability data from the US government for a further two.
"On 3 October 2014, the government commenced the process of purchasing two additional C-17A aircraft, and requested pricing and availability data for two further aircraft," a Defence spokesperson said.
"The [forthcoming] Force Structure Review will consider two further C-17A aircraft [a 9th and 10th C-17A]."
However a Boeing spokesman denied knowledge of any options and said that five of the 10 "white tail" aircraft it has privately funded remain for sale.
"There are no options, all five are currently available for sale," the spokesman said.
In addition to the Australia pair, Canada has purchased one aircraft and two have been sold to an undisclosed customer in the Middle East.
New Zealand is another country linked to a potential C-17 purchase, having recently launched its Future Air Mobility Capability program to replace its 50-year-old Lockheed Hercules fleet.
A Royal Australian Air Force C-17 performs during the Australian International Airshow at the Avalon Airfield.