Altair is the brightest star in the constellation of Aquila (the Eagle). It lies at a distance of approximately 16 light years from Earth, and its color is pale yellow.

The scientific community is very interested in Altair, as it is one the locations from which radio signals were received that have not yet been scientifically explained. (The signals were first received on February 17, 1990 by a Ukranian astronomer).

Altair plays a part in the Humanoid Galactic History. Its "civilization was colonized from Vega. The Altair civilization is quiet and contemplative, given the peaceful philosophic orientation. They are not currently involved in space exploration." (PoL)

Other sources, however, attribute it a more active role: According to Chuck Roberts and several other UFO related sources, the Altair system (also?) has reptilian inhabitants (lizzies) from the Draconian Empire. This is in line with ancient Earth teachings that also associate the Altair system with reptilians.
Branton, too, consistently confirms the presence of "collectivist greys" in the Altair system. However, in the Dulce Material, he also mentions a mixed group of inhabitants on the fourth planet of the Altair system, called Altaira. This planet would inhabited by a "nordic" (or blond) race that co-operates with a race of greys. He claims these are not part of the Draconian Empire, but they are heavily involved in abductions and in interbreeding programs (between these nordics and humans).
Another source, the late Dr. Michael Wolf, also mentions a race of 'human-looking' extra-terrestrials from Altair that would be in communication with the US government. He also mentions Altaira but claims it would be part of an organisation called 'The Alliance' which would be an alliance of Nordic Blonds.It's not clear whether this alliance is the same one Bob Renaud talks about, which is 'The United Worlds Alliance' of which Korendor allegedly is a member.

More information: Altair must have played an important part in Egypt, too: just as the three pyramids in Giza represent the three stars in the belt of Orion, so does the pyramid of Esna represent Altair.