Throughout the centuries, many people of all walks of life and in many countries have reported seeing UFOs. Ancient sightings are attributed to drugs or religious ecstasy and remain largely anecdotal. And sightings in the 20th century have been met with great scepticism, mockery and derision. Authorities have been less than straightforward in these matters, attributing sightings to phenomena clearly not in line with the events witnessed. Regardless of where you stand on the issue, one thing is true, a lot of people have and are seeing strange things overhead that many refuse to investigate. The National UFO Reporting Centre, based in Davenport, Washington, records an estimated 5,000 new sightings annually and keeps a database of 70,000 extraterrestrial encounters stretching back to the 1950's. Let’s take a look at the top UFO sightings.