Here are a pretty comprehensive list of many major countries around the world that have been studying UFO's for some time and are starting to declassify certain documents due either to transparency laws or public inquiry. Most, if not all important "details" have been blacked out, but you can see very clearly that our governments has been reporting sightings within its own structure for many many years now.
http://www.disclosureproject.org/cou...fo-files.shtml
One of the first links leads you to this recent release of documents by National Security Agency/Central Security Service of USA (
www.nsa.gov). In it it contains files on Unidentified Flying Objects appearing on radars that the military cannot explain. Most entries are blocked out, and only ones that contain "probably balloons" are left.
http://www.nsa.gov/public_info/declass/ufo/index.shtml (contains links to PDFs)