Now, I am no ufologist, but there can be no doubt that sometimes UFOs impinge on cryptozoology and other aspects of the paranormal; but that definition is not sufficient. Strictly speaking a UFO is any celestial object that cannot be identified by the onlooker.
UFOs could be explained in any of the following ways, some involving the paranormal, some not. Many cryptozoologists like to distance themselves from anything to do with UFOs or the paranormal, on the grounds that a "paws and pelts" explanation for cryptids is acceptable scientifically, while anything involving UFOs is not. I would disagree. We cannot say where the boundaries of scientific possibilities occur, though many would hold they know. This, I fear, is not due to knowledge or common sense, but due to a lack of imagination.
Anyway, putting all this to one side, let us have a look at what possible explanations for UFOs we can consider:-
(a) UFOs are objects misperceived or ehose nature is misjudged by witnesses. [I feel this may explain a great many UFO
(b) UFOs are extraterrestrial spacecraft, manned by beings from
outer space. [This, known as the ETH hypothesis, is a
particularly popular explanation among American
ufologists]. A variant of this theory is that they do not
actually contain extraterrestrials, but are robotic machines
that were originally dispatched by extraterrestrials.
(c) UFOs are ultraterrestrial, having their origin in another
dimension or universe. [This is not so strange as it may
seem. The possibility of the existence of other universes
is now receiving serious attention from physicists].
(d) UFOs are in fact secret aircraft used by an earthly
government or governments or even by non-governmental
(e) UFOs are sent out by technologically advanced races
beneath the sea or under the earth's surface.
(f) UFOs are hallucinatory.
(g) UFOs are projections or holograms.
(h) UFOs are the result of hoaxes.
There may be other possibilities which have not occurred to me. Of course, the explanations in this list are not mutually exclusive. It is quite possible that a number of them are true. But I do not see any of them as being less scientific than the hunt for cryptids. It is just that, for some of us, UFOs are harder to believe in than unknown animals. This, however, does not obviate the possibility that they indeed exist and the cryptozoologist should not scorn - or spurn - cryptozoological cases in which they make an appearance.
Due to some computer glitch which is beyond my competence to fix, there is a gap here. The next item is below.