That is one freaky close encounter. I know the credibility of two of the main witnesses has been called into question, but they were Air Force members, whose account of the physical elements of the sighting was corroborated by other high-ranking Air Force officials, so it's hard to believe they made up everything. It's quite possible that Jim Penniston embellished his story for personal gain, but there seems to be no denying that lots of other credible people saw something very strange.

With regard to your comment below about being able to suspend disbelief in the possibility of interstellar travel in order to support the possibility of intelligent extraterrestrials being the source of the UFO phenomenon, I'm with you. That is difficult to wrap my head around. But what if there is intelligent life within our own solar system? If UFOs truly are being built and piloted by advanced beings, then they are certainly sophisticated enough to hide themselves from our detection within our own solar system.

Or, if you really want to stretch your imagination, I'll defer back to the Rendlesham Forest incident and the claim by Jim Penniston that when he supposedly touched the craft with his hand, a vast amount of information was instantly transferred to his brain, including the message that the beings inside the craft were humans from the future. That's about as "far out" of a theory as I've ever heard, but I'm not sure it's that much more far-fetched than the idea that we are being visited by aliens from another solar system.