When authoritative reports of radical-design craft having spectacular performance are viewed in the light of a stream of astrobiological discoveries, the possibility that some UFOs are alien does not seem quite so farfetched. Serious-minded scientists in astronomy and other disciplines estimate there could be billions of planets in the universe, and millions that could harbor life. If even a few of those planets were occupied by technological civilizations, their ability (if not desire) to explore other worlds, such as ours, must be a possibility.