I have never seen an edge contrail before, or at least not one that looks like a beam of dark piercing the sky. I saw this one and had to pull over to take a picture because… what the?!? The line of shadow actually is more pronounced in the picture than what my eyes saw, so I’m glad I took it. And I’m glad for this article, from which I learned about contrail shadows. Although I’m still wrapping my head around how it works. The article goes through some complicated math. Regardless, a shadow line in a clear blue sky is rather striking. You can see a bit of the fluffy end of the contrail causing the shadow in the upper right of the photo.