No, UFO means Unidentified Flying Object, So it can be a lot of "things", by lack of better word.
People see strange lights which they cannot indentify as a terrestrial craft. So they conclude it has to be an extraterrestrial craft.
UFO's are seen in the daytime too. However, I think they are more "visible" in the nighttime because then the lights become clearer against the night sky.
Actually people do see UFO's on the Ocean. Only, a lot of people do not mention it because they are afraid they will be classified as crazy or just saw a kind of craft which is manmade but not known to them. I gather there are a lot of crafts in the sky which are just military flights by crafts not known to the public.
Still, there remain sightings which are not caught on radar or which disappear as rapidly as they appear.
What are they? Secret flights with new crafts which make testflights?
But does that go for all the sightings? There are strange phenomenon happening every once in a while for which there is no clarification.
How come? Where do these crafts come from?
Maybe, if it are extraterrestrial flights, the occupants do not wish to make themsleves known to the human race. I find this confusing and I'm curious to know what explanation is there for such sightings.
I know for sure that if I was an extraterrestruial, flying my spaceship, I definitely would not want to contact the public on earth. Look at it this way. You are in you spacecraft, hovering above earth and you see what is going on in this civilisation
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Would you land, with the risk of being captured immediately?
Oh well, I am dead tired. I hope it makes sense. If not, I'll be back after a good night sleep...
It is 5.15 am, and really time to go look for my bed.
Let's discuss it some more please...