Watching Rogan episode on UFO's, etc,
 These flying orbs or disks that can cloak (?) and move in ways no regular aircraft can.
      I've also 'heard' reports on 'aliens' walking on earth while being cloaked, but thats another story.

 Could be :

1. Aliens.
2. Time travelers from the future watching history unfold as it is.
3. Advanced developed technology nobody know about yet from country X.
4. Visitors from another dimension, not necessarily from outer space per se.