Instead of "many possible explanations", I'll change that to "many plausible explanations"...along with some very implausible ones. Have you considered, Wolfgang, that all these sightings may actually be due to injestion of dried banana skins, causing mass hallucinations?

No?

Oh, come on, surely that is much more convincing than the thought that hundreds of highly qualified people have actually SEEN something alien and intelligently controlled that we don't already know all about?