If even one of these unidentified UFOs turns out to be an alien craft, the impact on all aspects of our nation's culture-economic, political, personal-will be limited only by what is learned from an open, serious, objective study of the subject.

In those same decades, most UFO sightings were made in the daytime and frequently at close range, when shapes and surface features could be distinguished, thus making positive identification of normal sights easier and the descriptions of unusual sights more detailed. When all normal explanations had been eliminated, the witnesses could concentrate on those aspects of the experience which were most abnormal.

If every UFO report could be convincingly credited to some conventional astronomical or atmospheric phenomenon, there would be no UFO mystery. It is precisely because so many UFO reports cannot logically be blamed on stars, planets, satellites, airplanes, balloons, etc., that a UFO mystery has existed since at least the mid-1940s.

If even one of these unidentified UFOs turns out to be an alien craft, the impact on all aspects of our nation's culture-economic, political, personal-will be limited only by what is learned from an open, serious, objective study of the subject.

These abnormal aspects included the shapes of UFOs and their behavior. Most of the UFOs seen in the daytime were said to have had simple geometric shapes-discs, ovals, spheres, cylinders-and surfaces that looked like metal. Such shapes are not only nonexistent among known aircraft, but contrary to all known theories of flight, in most cases offering control and performance disadvantages rather than advantages.

For more than 50 years, men and women around the world have reported sights in the sky that are strange to their experience and understanding. Inasmuch as many of these sights appeared to be solid objects having impressive performance, they have become known as Unidentified Flying Objects (UFOs) or, colloquially, flying saucers. Their positive identification is one of the major public scientific challenges of the era, with a significant number of these sights so far defying all reasonable efforts at classification.

Hundreds of thousands of UFO sightings have been made by persons in all walks of life, in all parts of the world. Tens of thousands of UFO reports have been made to governmental and private agencies in the past 55 years. Thousands of these reports have withstood careful scrutiny and appear to represent real objects having a novel nature.