RAF Menwith Hill is a joint population base including Air Force, Army, Navy and Marines. The base also has a large DoD Civilian population along with major contractors from Lockheed Martin, Northrop Grumman and Hewlett Packard. Besides the U.S personnel assigned to the base, there is a large Ministry of Defense (MOD) workforce.
There are about 2200 staff from both UK and US. Approximately one third are British, drawn from HM Armed Forces, Civilian personnel, MDP and contractor staff. About one third of the US personnel are active duty military personnel representing all four services (Air Force, Army, Navy and Marine Corps); the rest are US civilians. The majority live off base and contribute substantially to the local economy.
The 421st Air Base Group is located at Royal Air Force Menwith Hill and is a component of the 501st Combat Support Wing headquartered at Royal Air Force Alconbury, England. The group is made up of 786 people assigned to the various squadrons throughout the group. The unit employs approximately 74 active duty military, 68 DoD Civilians, 72 Non-Appropriated Fund employees, 17 Local National Direct Hire and 61 contractors. 494 Ministry of Defence employees also work in the unit.