24 hours of flights

NASA -- You can follow the progress of air travel on radar through the US by looking at an animation of the US government collection. The number of planes in the air spikes during certain hours. Use the toggle button in the movie fileto scroll back and forth through the animation.

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John Walkenbach -- "24 hours of flights"
Bonus Link: BBC programme citing US scientist David Travis researching "whether the vapour trails left by aircraft were having a detrimental effect" on the atmosphere.
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