Since the late 1940's sightings of strange lights in the sky and unidentified flying objects have been seen from the deserts of the American Southwest to Siberia. For decades researchers and scientist alike were baffled as to the true origins of the craft. Many believed these craft were visitors from the planet Tralfamadore. Others began to examine the problem from a scientific perspective and, over the years, have been able to account for well over 99 percent of these sightings.
There are several underlying scientific principles at work. Chief among these are Occam's Razor and Extraordinary Claims. What is a more likely explanation for strange lights in the nighttime sky: A Boeing 737 illuminated by the setting sun or an alien space craft? A classified experimental military airplane or little-green-men on spring break from Mars? A sauce pan on a string or superman visiting from Krypton?
UFO proponents also fail to show any real evidence. They make extraordinary claims, yet cannot provide extraordinary evidence to support these claims. The diehard proponents will point to a worldwide governmental cover-up. However, if they were really being honest with themselves they would realize that the government is leakier then the Titanic. Surely a Wikileak cable or former conspirator would have surfaced by now with a little-green-man in a jar or a piece of a flying saucer.
In the end a vast majority of UFO sightings can be explained away as hoax, natural phenomenon, or earth constructed aircraft. No real evidence exist to the contrary.
Below is a great link to a video about UFOs and likely explanations: