Are these planes flying at Area 51?

Regardless of our personal convictions about UFOs, activity appears to have picked up again at the legendary Area 51. But as always, the question remains: What is it?

An article in Popular Science speculates what may be going on in the storied parcel of desert in southern Nevada, ideas that include the construction of specific models of futuristic warplanes. Perhaps the most interesting part of the post is the gallery of artist renderings depicting possible flying machines, based on various forms of evidence ranging from patent filings to reported sightings.