U.S. Government UFO Document:
The Office of the Secretary of Defense
and Joint Staff Reading Room:
“Unidentified Flying Objects (UFOs) Related Documents”

At the below link one can find a second U.S. Department of Defense Web page that presents the claim that the U.S. government (U.S. Air Force) ended all UFO investigations on 17 December 1969.

In addition, the Web page presents many U.S. DoD and UK Ministry of Defence UFO documents:

http://www.dod.mil/pubs/foi/ufo/