While the modern history for UFOs began in the late 1940s, mysterious objects have been observed in our skies since the earliest days of recorded history.
There have been reports of mysterious flying craft up through the beginning of the World War 2, these were knicknamed "Foo Fighters" by the pilots, as they appeared like glowing balls that performed aerial maneuvers far beyond the capabilities of those observing them buzz around their aircraft. The American's thought that it was the Germans who had developed some new weopons to use against them but the Germans thought that it was the US that had the new technology.
All of this leads to the day when there was a crash in a remote part of New Mexico. Believed by many to be an alien spacecraft, the U.S. government has gone out of their way to explain this away as nothing more than a crashed weather balloon. But there were to many witnesses that saw the crash and handled the debris, many in the "clean up" observed the bodies of the little occupants.
During the 1950s, many UFO sightings were reported around the world. So many of these reports were coming in from reliable witnesses that the Air Force was publically forced to take notice. They surely couldn't let the American public think that they weren't interested in what surely posed a threat to National Security. Then began a series of official UFO investigations by the Air Force, first it was "Project Sign", then it was "Project Grudge", finally the most famous "Project Blue Book" in 1969. "Project Blue Book" was officially closed down in 1969, due to lack of evidence linking UFO's with any kind of threat to the United States National Security, so the Air Force pronounced that there was nothing to UFOs and that they could be explained as swamp gas, weather balloons, or planet Venus.
On October 5th 1960, a formation of UFOs were seen by early warning radar in Thule, Greenland with a heading that seemed to be coming from the Soviet Union toward the United States. Within minutes, SAC (Supreme Allied Commandment) crews around America were scrambling to their nuclear weapons and B-52s. When SAC Headquarters signaled Thule for further confirmation, their calls were answered with silence. Had Thule already been taken out? Anxious moments as the Generals prepared to send the B-52 crews to their targets inside Russia, when suddenly the radar blips changed course and disappeared.
The UFO phenomenon has continued up to modern day. Many things are linked to this mystery, Abductions, Cattle Mutilations and Crop Circles to name just a few, this subject screams out for a proper investigation, as Budd Hopkins (an Abduction UFO Researcher) puts it "an extraordinary phenomenon deserves and extraordinary investigation".
Thanks to the Freedom of Information Act thousands of pages of documents have been uncovered by researchers showing that each branch of the military, the FBI, CIA, NSA, etc have kept a very close watch on what is flying around our skies. Some researchers think that not only does the US Government know about UFOs, but has actually interacted with the intelligences that fly them.