A clip from the film Unacknowledged mentions a possible link between sightings at Nuclear facilities and UFOs/UAVs.

Certainly there is no clear indication these UAVs/UFOs are at odds with humanity, if these entities are indeed a higher lifeform there is no doubt of their ability to eliminate humanity. As some on these black projects have indicated there is the possibility that these events could be manifesting for a reason, albeit as yet unknown to us. In the meantime, the news media is clearly attempting to spin this into an invasion type scenario, even if there is no clear evidence to support this claim.

This article at UAPNEWS, mentions an interesting hypothesis as to how these objects could be interdimensional craft, which is why sometimes they appear and disappear from view, as well as why they can sometimes look like spheres. It could be very interesting to see where these sightings are headed, perhaps the truth will reveal itself in time.