A aeroplane is a UFO until your parents tell you what it is. If you have parents and if they know what it is and if they tell you.
Ball lighting might appear to be 'flying', driven under it's own power and, in a sense, it is.
And probably also mistaken for an object directed by some kind of intelligence. In the sky.
Did I mention that it was darting around faster than any man made object could? Wow, that was a UFO!
The classic sceptical response is to ridicule the notion, the very notion that it could be aliums.
Sceptics get a bad name as obnoxious pricks for exactly the above kind of misappropriation of intent behind statements which contain words that have become so loaded by their own personal philosophical drive, they fail to maintain any consideration of impartiality in their response.
The quick absence of any consideration that any kind of conscious uncertainty could exist in the mind of the observer who dared to describe an object she couldn't identify, often makes good faith communication with them difficult.
Bad those are just bad sceptics, not representative of the real sceptics. Not real, (dare I say) Scottish sceptics. [unpack that!]
Let me tell you, real sceptics. You are woefully out-fucking-numbered.