Human history and many narratives in ancient civilizations contain several myths and legends of extraterrestrial stories and visitations of aliens on Earth. Over the thousands of years many different cultures have regarded meteors and comets as supernatural phenomena. In the last century Unidentified Flying Objects (UFOs) sightings, especially by the US Air Force, attracted the attention of newspapers and media as well the US army and NASA. For most of UFOs narratives there are great similarities between certain religious symbols. Such images of UFO phenomena are documented by art historians placing more conventional religious interpretations on such images. In the past 70 years NASA and US military agencies investigated the possibilities of UFOs to be connected with extraterrestrial visitations. All reports and inquiries by special teams of scientists concluded that there is no positive evidence of extraterrestrial presence. Only a very small proportion of UFO sightings are unexplained aerial phenomena. A symposium of American Association for the Advancement of Science (AAAS) in 1969 organized by the famous astronomer Carl Sagan found that there was no evidence for extraterrestrial involvement in UFO sightings. On 14 September 2023, NASA (USA National Aeronautics and Space Administration), an independent agency of the U.S. federal government responsible for the civil space program, aeronautics research, and space research, released a report by an independent study team that looked at how and why NASA might want to be involved in studying Unidentified Anomalous Phenomena (UAPs), which in the past were named UFOs (Unidentified Flying Objects). The group of scientists announced that “…At this point there is no reason to conclude that existing UAP reports have an extraterrestrial source”. The USA government agencies and other countries (Russian Federation, China, UK, etc) have a long history of assessing unusual objects in the sky. Especially in the USA reports were stretching back to military investigations into reports of flying saucers in the 1940s. This review presents also information on the Fermi paradox. Where are the aliens? The Institute for the Search for Extraterrestrial Intelligence (SETI), a radio search for signals that would prove the existence of other intelligent beings in the cosmos (NASA/SETI programme). The Drake equation, following the project Ozma, the formula that can conceivably calculate the number of intelligent civilizations exist in the universe, taking into account certain parameters.