The most common alien race visiting us are called Greys. The alien type used in the Alien Autopsy film aired by FOX television in 1996 was a Grey. Numerous reports of Abductions are reported each year. These cases have been increasing substantially since the 1950's. Many people believe that the governments of the world are involved in much of the activities that go on.
Beliefs range from direct involvement to an involuntary indirect involvement.
It would appear that only certain levels or branches of the government have intimate knowledge of what is going on. Allegedly there are many secret locations around the world that the governments use to hide their knowledge and activities. The most prominant location being a place that doesn't exist, Area 51 . It was highlighted in the movie Independance Day ID4. Wright-Patterson AFB is one of the first places used to store information.