How many times have lenticular clouds been reported to local news and law enforcement agencies as UFOs? Who knows?
What they generally mean, though, is high winds aloft.
If you imagine the wind flowing over the mountains much like water or a wave might flow over a barrier of rocks–with the resultant downstream ripples that get progressively smaller–you’ll have an idea of where these lenticulars tend to form. At the crest of each wave, if there is enough moisture in the atmosphere, you can find lenticulars (also called “wave clouds).
Their origin aside, they certainly make for some interesting photographic subjects.
Here is one for a UFO report:
