UFO: Enemy Unknown

In the year 1998, the amount of reports of UFO sightings has been drastically increased. Stories about abductions and alien attacks became more and more widespread. Finally, after various nations of the world have failed to intercept the UFOs, their representatives met in a conference of global importance in Geneva, Switzerland. It was eventually decided to organize a secret paramilitary group, dubbed Extraterrestrial Combat Unit (X-COM). Starting with one base, two fighters, one transport, and a few soldiers, X-COM must locate the aliens, learn about their origins and technology, find out where their base is, and destroy it.

Source: TheGamesDB