Anything that flies through the air and is something that we cannot identify is defined as an Unidentified Flying Object or UFO. By its very definition, a UFO is real. It is just that we cannot place it in our understanding of known flying things, be they clouds, lighter or heaver than air craft, flocks of birds, or weather and electrical phenomenon.
The problem with the term "UFO" is in the evolving and migrating word usage and understanding. The term is mistakenly and automatically associated with alien or unearthly superiority in creating technology that mankind could not have possibly done. And now that technologies are available to create Aeriel images by creating shaped clouds or by literally writing on clouds to create advertising in the sky, we are in a world of hurt, when it comes to unidentified flying objects!
Nothing can be ruled out in terms of alien or even hidden and superior Earthbound civilizations. The probability of UFOs being of other worldly origin makes fine logic, especially when their appearance and actions are described by stable and reputable individuals, including astronauts, soldiers with high security clearances and law enforcement. It is perfectly logical that there are other living civilizations that have technology that we simply cannot make or understand.
UFOs are also mistakenly associated with claims of being kidnapped by aliens and subjected to all sorts of actions. Frankly, those claims are far better off in the realm of psychotic and other mental disorders, as they are far too close to the traumatic memories that come from being in hospitals and undergoing medical procedures, from watching them on television and in the movies, or from visiting and observing while others undergo them.
Psychologist Susan Clancy, in a Harvard Gazette article, introduces the concepts of sleep disorders, including sleep paralysis, lively imaginations, and false memories from a bad night's sleep as explanations for the alien abduction stories. In addition, there are clues from the individual's other personality and behavioral issues, such as a pre existing heavy interest in the subject of aliens, inability to socialize, and other proclivities toward fantasizing. Sometimes, the brain comes up with a detailed dream, visions, and memories, in order to reconcile multiple disturbing and unresolvable worries, especially with the unexplained facets of nature.
So, UFO and alien go hand in hand in our imaginings, and in our suspicions that such sites as Area 51 and other secret underground facilities are massive coverups for long term interaction and cooperation with aliens, but it is fairly clear that humans just cannot keep a secret, and many of the tens of thousands who have worked in our top secret facilities either have never been exposed to all information, or simply would have leaked something by now if all of that was going on.
In summary, UFOs are quite real. It is just some of the explanations for them that are unreal.