The presence of the United States Air Force at RAF Fairford is, as with all bases made available to United States visiting forces in the United Kingdom, governed by the NATO Status of Forces Agreement 1951 and additional confidential arrangements.
Her Majesty's Government have to be fully consulted and agree before any UK-based US forces are deployed operationally. The Joint Churchill-Truman Communiqué of January 1952 stated:
“Under arrangements made for the common defence, the United States has the use of certain bases in the United Kingdom. We reaffirm the understanding that the use of these bases in an emergency would be a matter for joint decision by H. M. Government and the U.S. Government in the light of the circumstances prevailing at the time.”
The use of the US military facility at Diego Garcia is governed by an Exchange of Notes between the US and UK which requires the US to seek prior approval for any operations that they wish to undertake from Diego Garcia.