Unidentified flying object

Unidentified flying object (UFO), object or light reprotedly seen in the air during day or night that cannot always be explained by conventional phenomena. Though many UFOs are found to be objects, such as weather balloons or satellites, or the result of atmospheric conditions, there are certain sightings that do not fall into any known-phenomena categories. The U.S. government continues to investigate thousands of such reports and to sponsor scientific studies on the subject.