Over the past 60 years or so the notion of flying saucers and small human-like figures with pale skin and large black eyes have really become popularized because of increased communication, improved recording technology like cameras, Hollywood depictions and perceived government cover-ups to keep conspiracy theorists entertained. But there is evidence that these entities have been flying around earth for several thousand years as ancient artifacts depict them.
So we have to ask ourselves what are these objects that have flown in the sky for anywhere between 60 and 4,000 years? Although science still speculates that there could be life living in oceans in some of Jupiter's and Saturn's ice covered moons, the possibility of intelligent life in another part of our solar system seems very remote. So for these spacecraft to be from alien life forms that would imply a species so advanced that they have mastered interstellar space travel.
To speculate on these entities being aliens is easy from our perspective as the people on the host planet. But we have to take this from the other point of view. Let's say that our race becomes so advanced that we master interstellar space travel and we find a planet with intelligent life on it. Even in the largest, most advanced space vehicles we would be cramped and just aching to get out and explore. If we see a planet we will either try to land and use its resources for our survival, make contact with any intelligent life on the planet, or move on. We're not going to spend 60, 100, or 1,000 years floating in the night sky, coming down every once in a while to probe the occasional planet-dweller.
The assumption that these are alien life forms out there is an arrogant position to take. We're just not that special to command being watched over by some advanced alien species with nothing better to do with their time. More likely these entities have some sort of special tie to this planet. These are some of my ideas on what these beings actually are:
1. Some kind of military android with an advanced flying machine. This would explain military interest and secrecy in these activities over the last 60 years but it wouldn't explain sightings hundreds of years before then or why it's taken 60+ years for the military to perfect this technology.
2. Spiritual beings, either angels or demons. A lot of Biblical accounts have similarities between them and the whole abduction experience. I agree with a lot of the ancient alien theories out there except I think they have it the other way around. They think Biblical and other religious or mythical texts were actually describing alien encounters. I think the Biblical accounts were right and the encounters some people are having today with these beings are spiritual ones. Jesus' return to earth could very well take place in what we consider to be a spaceship but is actually the connection between the spiritual world and the three dimensional world.
3. A civilization that has once lived on the earth in the past and decided to come back for a visit to find that an asteroid destroyed any remnants of their race along with the dinosaurs and they see a new intelligent race has taken over. This would be somewhat similar to the Nibiru/Annunaki argument, except I don't believe there's some Earth-sized or greater planet in our solar system that we haven't officially discovered yet. This theory would explain why there are artifacts discovered on this planet that are up to 2 billion years old that had to be made by intelligent beings.
4. A very advanced human species that has mastered time travel. They have a great interest in their origins but they realize that they can't mess with the order of time too much so they have to remain in hiding as opposed to making direct contact with their distant ancestors. I don't like this theory in that we'd have to give up a lot in terms of looks and physical strength as a species in exchange for intelligence.
5. Some kind of interstellar craft sent by life on another planet, but the beings running them are actually artificial intelligence, which explains why they can handle thousands of years of observation without being uncomfortable or bored. Still even with this theory, you'd think 4,000 years of observation would be a little bit of overkill.