The C-17, which will be purchased through a £130m contract with the Boeing Company, can carry the equivalent of three Warrior armoured vehicles, 13 Land Rovers, one Chinook, or three Apache gunships, enabling the RAF to get the right equipment to theatre rapidly.
As well as being able to carry loads of up to 75 tonnes and fly long distances (up to 2,400 miles) the C-17's ability to land on unpaved airfields in remote, land-locked regions make it a versatile transport aircraft, equally suited for a variety of missions.
Baroness Taylor said:
"The C-17 is a versatile aircraft which provides vital support to our Armed Forces. A sixth C-17 will greatly increase our ability to transport troops and heavy equipment quickly to operations.
"Our existing C-17s have already proved their worth around the world supporting UK operations in Iraq, Afghanistan, and in providing humanitarian aid after the Tsunami in SE Asia and the earthquake in Pakistan."
The RAF purchased four leased aircraft and a fifth C-17 last summer. The contract for a sixth, announced by the Secretary of State Des Browne through a written ministerial statement on 26 July 2007, will give the RAF a guaranteed long-term capacity in this area.
The new C-17 aircraft will join the rest of the fleet at RAF Brize Norton in Oxfordshire when it enters service in summer 2008.