What do you guys think of UFO's?

[Your Computer]

What am I saying is that it's almost impossible to ever meet them. Considering that it is proved there is not any habitable planet in our solar system and that the nearest star is approximately 4,3 ly away which is 4,06802721 × 10^13 kilometers then, excuse me, but NO!

"Habitable" is defined by our experience. There are assumptions attached to it that wouldn't necessarily apply to every possible organism in existence. Even if a "habitable" planet existed billions of light years away, if in fact these aircrafts are driven by aliens from outerspace, you would have to accept that it is in fact possible to travel at humanly-impossible distances and our knowledge of physics may be denied. Unfortunately, we don't know who drives these aircrafts, but that may be revealed some day.