UFO stands for Unidentified Flying Object. Although many people associate this term with aliens or spaceships, it can pertain to any unknown object seen in the atmosphere.

It is commonly believed that UFO sightings began in modern times, but sightings of extraordinary lights and mysterious objects in the sky have been documented for thousands of years. One of the earliest sightings was in the fifteenth century BCE, in Egypt, where "foul smelling circles of fire and discs in the sky" were observed. Centuries later, in 1516 CE in Nuremberg, Germany, more than 200 UFOs of differing shapes, including cylinders, spheres, and spinning discs, were observed. These examples typify the thousands of sightings that have been recorded over the ages in many different cultures on various continents.

The most interesting part of UFO history has been the latter half of the 20th century. During World War II, fighter pilots reported many luminescent and cylindrical UFOs. Sightings of these objects were described by both pilots and high-ranking intelligence officials. Interestingly enough, both the Allies and the Germans recounted this. At first, they both thought that these UFOs were really just new weapons made by their enemies. However, when they realized that the other side was seeing them, too, they concluded that these sightings were UFOs. Both the British and Germans created committees to investigate. Ultimately, it was determined that these UFOs, nicknamed "Foo Fighters," were not manmade; no alternative explanations were offered.

In the late 1940s, following WWII, the "flying saucer" era began. In 1947, a man named Kenneth Arnold recounted seeing "nine silvery circular objects" in the sky. He told his story to many people, including the press. He eventually wrote a book, titled The Coming of the Saucers. In it, he described the UFOs as flying saucers because they were shaped like large dishes. After the book's release, more and more people reported UFO sightings. Previously, anyone who reported a UFO was considered a liar or a lunatic. However, because authorities were receiving countless reports, they decided to set up a committee, called Project Blue Book, to investigate these sightings.

In the 1940s, the most famous UFO case in US history, the Roswell Crash, occurred. In early July of 1947, an object crashed onto a sheep ranch near Roswell, New Mexico. All the pieces of the fallen object were collected by members of the US Air Force, stationed at Roswell Army Air Field. Later in the day, the commander of the base informed the press that the remains of a "flying disc" had been recovered. This news spread worldwide in a matter of hours. Strangely, a few hours after the press release, the commanding general of the Eighth Air Force issued a counter press release asserting that the remains were from a common weather balloon. This retraction caused a lot of controversy. There were reputable eye witnesses including the sheep rancher and an Air Force major who saw many items of unknown origin made of strange material. They even claimed to have caught sight of bodies of non-humanoid beings.

Despite this incident and continued UFO sightings, the government disbanded the Project Blue Book committee in 1969, due to lack of concrete evidence. To this day, many people think the government is suppressing the truth of what they collected from the Roswell Crash and of other unexplained sightings and incidences. Over the years, UFO sightings have continued to be reported by people all over the world, including former US president Jimmy Carter, NASA engineers, and Japanese businessmen. In fact, it is estimated that every three minutes, there is a UFO sighting somewhere on the planet. Though most certainly there are a number of explanations for these UFO sightings, natural or otherwise, more research into this phenomenon is definitely needed.