[Rokke]

"Absolutely, one can ONLY be 100 % certain it was a vertical plume: the shaded side away from the setting sun is FACING EAST. On a contrail, the shaded side away from the setting sun is facing UP, where no human can see it unless they are in an aircraft ABOVE the contrail looking down."

So based on what you're saying, I shouldn't be able to find a picture of a contrail taken during sunset that has shading. And if I do, it must be a vertical column. Or am I not reading you right. Similarly, clouds pictured during a sunset with a shaded side must be vertical columns. Right? Because with respect to sunlight etc, there really is no difference between a cloud, a contrail or a trail of exhaust.

[Finny]

The side that is most brilliantly lit is the side facing the light source. The side that is the least lit -- the side in darkest shadow -- is the side facing the opposite direction of the light force. We are dealing with cylindrical columns; half of the column is facing the light source, and the other half is facing away from it. You know from which direction the light source originates. THAT knowlege, and that knowledge ALONE, tells you your POV and whether the column is horizontal above that light source, or vertical to that light source.

That's all you need to know to answer your own questions. It is not opinion, it is not interpretation, it is material reality.

[justa-hairyape]

And if I do, it must be a vertical column.

Unless it is taken from another airplane at similar or higher altitude.

Image of contrail must be taken from a camera no higher then the max altitude for that helicopter during filming. Must be during sunset. The other caveat is the plane contrail cannot reach horizon exactly where the sun has set. Almost the entire suns disk must be below horizon. The airplane contrail you are filming must be above 30,000 feet. Those are the same general conditions.

Physics is physics. Geometry is geometry. Cannot be denied. 100 % missile. That is all the proof you need.