The handover took place Friday at the company's final assembly line in Long Beach, Calif.
"I'm honored and delighted to deliver the Royal Air Force's newest C-17 to join the fleet at Number 99 Squadron, where our seven C-17s are in constant demand flying missions in support of [the Ministry of] Defense and other government agencies' requirements," said RAF Wing Cmdr. David Manning, officer commanding 99 Squadron.
Britain's first C-17 Globemaster IIIs entered service in 2001. Because of heavier-than-expected demand for their use, the country's Ministry of Defense ordered additional aircraft. They were delivered in 2008 and 2010.
Boeing said it received the order for the latest aircraft in March.
"RAF C-17s are ever-present when there's a need for humanitarian relief or peacekeeping around the world," said Bob Ciesla, Boeing Airlift vice president and C-17 program manager. "We're proud to support the Royal Air Force in providing for the mobility needs of their great nation, and we are grateful for the partnership with the U.K. Ministry of Defense and U.S. Air Force that made this delivery possible in such a short time."