I’m not a UFO believer; nor the opposite. Certainly there are many unidentified flying objects out there – but to jump from unidentified to identify it as alien craft is a big leap. I’m sure even the most ardent UFO believer will agree that a UFO does not equal a flying saucer with aliens in it.
Most of us have had first-hand experience of an aeroplane, for example, or even flown in one. Therefore, we can pretty easily identify an aeroplane – even if it’s so far away as to be only a dot in the sky. But to say a UFO is an alien craft is based on WHAT knowledge of alien craft? (Usually by claiming that it moves like no man-made craft – which still requires that you know of all man-made moving things in the sky.)