what is the reason for x's over the sky left by jets? Is that a chemical trail or shield to buffer satillites?

Answer 1

Jets burn fuel similar to gasoline. The fuel is made of carbon and hydrogen atoms, so when it burns it makes carbon dioxide and water vapor (H2O) as the waste product. When the water vapor is shot out the back of the plane it condenses into fog and leaves a cloud trail. Usually there is wind that rapidly spreads out the cloud but sometimes the atmosphere is very still and the trails can be seen for a long time.

There is some worry about the amount of water vapor that jets are putting into the high atmosphere. Some evidence suggests that it actually is affecting the earths climate. This was discussed in a NOVA program on TV "Dimming the Sun"

Answer 2

Just a vapor trail left by jets. Doesn't affect satellites.
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