If you study the image, you can see the shape of the United States.

Flight patterns, visualized (FAA, that is).

From the source:
The following flight pattern visualizations are the result of experiments leading to the project Celestial Mechanics by Scott Hessels and Gabriel Dunne. FAA data was parsed and plotted using the Processing programming environment. The frames were composited with Adobe After Effects and/or Maya and the final piece was highlighted at SIGGRAPH 2005 in the NVIDIA Immersive Dome Experience.