Unidentified objects aren't simply restricted to airspace. There are plenty of vehicles that people see that they have absolutely no clue what the hell they are, particularly non-gearheads. Take this orbital invention, for example. This "time machine," as it was labelled, has been causing quite the ruckus on Reddit, after somebody spotted it outside of a Best Buy. Shortly after, there were two answers to the rounded enigma that looked like it was from 346835497. Somebody posted more pictures of it, explaining that it was his father's boss' concept car. Also, a commenter linked to this, which explains that it's actually called an Extra-Terrestrial Vehicle.
Basically, it's a kit. A kit that has been seen on eBay anywhere from $50,000 to $86,000. Whether it can actually travel time, we're unsure, but we're not sure we want the future to come, if cars look like this.