Pharting & Phlying

I heard a story that when Air Stewards & Stewardesses need to <ahem> fart, they just walk down the aisle, talking loudly to cover up the sound.  And apparently they call this "crop dusting".

This exhaust trail from a plane could be the result.

If you are convinced, however, that this is more evidence of "Chem Trails", I think you might need a lie-down more than I do.