Why do UFO's spin?

Looking at the various reports and films of flying saucers, the question arises in my mind, why do some spin? There must be some advantage to it. I even remember film of a cylinder in Soviet airspace, that corkscrewed away, pursued by fighters (See gun rifling for the same effect with bullets i.e. spiralled chamber). We know from their antics that they have some anti-gravity mechanism that allows them to float in mid-air and various shots that seem to suggest short leap teleportation but nobody as far as I know has asked this obvious question or answered (correct me if I'm wrong). There was a question in The New Scientist's Last Word column about why a bicycle is hard to balance and keep upright when stationary but requires little effort when moving. An engineer from some university came up with a really ludicrously complex and totally erroneous answer in my opinion, missing out the simple fact that forward momentum cancels out gravity as long as you are centrally balanced. The same thing is true with spinning tops, balanced on a point - the pull of gravity is equalized all the way around as long as there is momentum driving the top forward, keeping it in place. This point is easily demonstrated by rolling a coin along the ground - as momentum fades gravity starts to pull it to one side in a spiral as we see with liquids (3-D version of this): See books by various authors on Viktor Schaubergers work for follow ups to this. Gyroscopes come into this as well, not only as glorified spinning tops but because of work by people like Eric Laithwaite and other engineers that pinpointed how this spinning motion could be utilized by flying saucers, even if only accidently by inspiring people like me in the UFO field.