Actually there is considerably more evidence to the existence of UFOs than there is of Bigfoot, for example docuemented reports of strange aircraft. Secret experimental aircraft? I'd buy that, but how come none of our fighters in the past fifty or sixty years have remained the same and never taken such a shape, even VYOL aircraft such as the Harrier and Osprey?
I refuse to let go of the possibility that in the universe, which is far too vast in scope for us to explore, we are it. That there is no intelligent life out there. Truth be told we could use it soon if it exists as we are quickly running out of it here.