First, you define UFO?
The proof of existence is in your sentence. Do you actually believe there is no such thing as an unidentified flying object?
I'm sure you mean to question the existence of alien craft from outer space, and I join you in that, but there is no question that there are things flying about unidentified. Many of them are even ours.
The air traffic controllers had an object on their screen (topic of the thread). It was flying (it was on and off the radar and had been seen by pilots near it). It was unidentified.
Ergo, it was a UFO.
Now do I believe it was from another solar system far, far away? How the hell would I know?
Was it piloted by extraterrestrials? How the hell would I know?
For that matter, how the hell would you know?
I don't know, you don't know.
Better keep an open mind, because there are things that we just don't know...yet.
That said, there are theories and opinions all which carry various amounts of weight and some of which are supported by sound arguments (on all sides of this issue).
How hard does an analogy have to bite you before you realize it relates to the discussion?