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"It's like it's spraying out of the top of it's wings" - No shit, Sherlock. Lift is generated by having a relatively flat under-surface and a rounded upper surface with comparatively more surface area that creates 'drag'. Since air passes under the wing with less impedance, a vacuum is generated above the wing resulting in lift. Additional moving parts are used to control a planes changes in altitude by essentially altering the shape of the wings.

Here's an overview of the parts of a plane NASA has put together for grade-school students - http://www.grc.nasa.gov/WWW/k-12/airplane/airplane.html

Now consider driving through a fog, which is basically ground level clouds. We should all know that clouds are mainly water vapor. As such, we usually have to turn on our wipers to clear the windshield of the condensation. Apply that to the airplane scenario, and where is the water vapor going to condense and trail? On top of the wing where there is greater resistance, and more surface area on which to condense, of course. Why would it seem to turn on and off? Partly due to moving through more water laden air - just as driving through fog it's not of uniform density, as well as the adjustments being made to change or maintain altitude.

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