British Prime Minister David Cameron, speaking in Parliament this week, said the aircraft "is becoming an absolutely brilliant workhorse for the (British air force) in terms of bringing men and material into a war zone like Afghanistan but also evacuating civilians in times of need."
The aircraft being purchased will become operational with the air force in July and will ferry troops and supplies to Southwest Asia, where British forces are part of the International Security Assistance Force.
In addition to the regular ferrying of troop and supplies, Britain keeps one of its C-17s on continual standby to evacuate wounded personnel from Afghanistan.
Britain is paying about $316.5 million for the aircraft.
The C-17 Globemaster III was introduced into service in 1993 and is operational with five military forces around the world, in addition to the U.S. Air Force.