Here’s a fascinating video of air traffic across the globe during a 24 hour span condensed down to about 2 minutes. It was taken by an orbiting satellite and includes the day/night footprint gliding across earth. The yellow represents large jet flights from the major carriers. You can see aircraft landing in Europe having left America, and then returning to America from Europe. When you see all the planes in the air you realize what an challenging task it is to keep it all organized. We all like to complain about flying, but the pilots, airlines and air traffic control really do a pretty solid job it keeping us safe.
On September 11, 2001 all air traffic was ordered to land once the government got a grasp of what was happening. This grounding was unprecedented. I remember that I had to get away from the heartbreaking television reports for a while and so went to lunch with a friend. We at an outside table of a small bistro and gazed up at the perfectly clear, blue sky. I live in Chicago, a major airline hub, and are used to seeing planes all the time. But on this afternoon we could not spot one jet or contrail due to the grounding. It added to the eeriness of the day.
The following is an animation of all planes landing on September 11, 2001. Click the image to open it in another browser window to see animation.
This photo below shows a midwestern shot of an empty sky, save three jet contrails. They are Air Force One and two fighter jet escorts.
Images, Videos and Gifs: U.S. Government, NASA