Film Theory: The Aliens In Signs Aren't What They Seem...

Taking a look at the alien's appearance then, they are indeed pretty demonic in nature - with black eyes, sharpened claws, and scaled skin, blending into their surroundings with a supernatural stealth.

For aliens, it seems strange that they would opt to not take advantage of their technological superiority over humans that got them to our planet in the first place - but for demons however, it makes perfect sense for them to simply use the tools of their body, built to torture and frighten humankind in equal measure.

To reinforce this point, we never actually see the spaceships these creatures are supposed to have arrived in. Instead, we’re only shown lights in the night sky - with a single bird flying into the cloaking mechanism representative of the ship being invisible in the day time. These lights almost look like pairs of demonic eyes looking out of the darkness, fashioned in a way that brings up images of cartoon evil watching from the safety of night.

It could also be a visual representation of burning in the sky - that even Heaven isn’t safe and is under attack from these Hellish creatures, and looking to God only serves to look at the devil in some biblical rendition of a test. When everything around the characters seems like an unstoppable force of evil, they’re going to have to look deeper to find God once more. Birds falling from the sky are also one of the signs of the apocalypse. The more you know.