There is no question that there are a ton of planes in the sky at any given point. Understanding just how crowded the skies are requires more than just a bird’s-eye view, so someone took a satellite-camera view and turned it into a nifty video.
As the shadow of night passes over the different continents, it’s clear that flight patterns are based upon the sun. Many flights leave the US east coast in the middle of the night, flying against the shadow to land in Europe at dawn. Heading west, there seems to be no reason to go against the shadow, so the vast majority of congestion in the air happens from morning to evening.
Judging by the position of the shadow, this video was likely made in the spring. Regardless of when it was made, it’s a nice way to visualize what’s happening up there. Enjoy.