There is no official data or record about the UFO sighting. But according to folk tales and in colloquial manner, it can be said that people does observed such flying objects since historic times. The first sighting of UFOs is marked since late 1800 by most of the researchers. The most famous and prominent UFO sighting was made in the year 1947 by private pilot Kenneth Arnold. He claimed to observe 'flying saucer' in the sky. This event led to the reporting of similar reports in different parts of the world at different times. According to a rough estimate, about 60% of such reports are hoax or due to some other reasons. While, some of the objects noticed in the sky were definitely astronomical in nature like comets, asteroids etc. But then some were also a result of disillusion like perhelia and lenticular clouds. There are certain natural phenomenons that give rise to various hypothetical shapes formation on the astronomical horizons. Most of these halos are perceived by naked eyes and are called as UFOs by populace.
However, a good amount of 40% cases are still left to be researched. There are enough evidences that rule out all the possible human errors, psychological aspect and hallucinations. The reports do claim the presence of extra terrestrial components in the earth's atmosphere on scientific analysis also. The marks that are supposedly left by an alien spaceship at grounds, known as 'trace case' are often reported by the people. Such incidents are reported mainly by the inhabitants of remote and rural areas.
Scientists and researchers are working extensively to mark the presence of life on other planets and their possible intervention in earth's atmosphere. However,