The seas between Europe and North America are relatively quiet on any given day, but 30,000 feet above some 2,500 planes follow tracks (like invisible highways) between both continents, landing in gateway cities like London and New York or flying far beyond. Of course, not all of those aircraft are carrying commercial passengers -- cargo, military and private flights make up a great deal of that traffic -- but regardless of their purpose and destination, that kind of volume is a spectacular sight to behold. NATS, the UK's National Air Traffic Services, created a video render to help visualize the 1,400-odd flights it handles each day. The agency helps provide aircraft separation via pilot reports rather than radar, which is only accessible to flights near land. With limited technology at their disposal, it's a lot of work for controllers, as you can clearly see in the video after the break.