It's an absurd idea. Even if intelligent life were to exist else where in the universe that doesn't mean it would have the technology for intergallactic travel, have any desire to explore the universe, or even be able to move themselves. Without impossible faster than light travel if such civilizations did exist they would not be able to even reach us.
Also, if an alien race had the technology to travel the stars and reach Earth why would they hover up in the sky. Why wouldn't they either reveal themselves to us or at least figure out that putting useless flashing lights on their aircraft tends to sort of blow their cover if they're trying to remain hidden.