Here's an interesting one: a contrail with a shadow that reaches the ground. Is that a thing? (I've never seen such):-

Iain Cameron seems to imply he saw the black line before he took the picture, which would rule out a camera artifact?

With the exact time, we could identify the aircraft and the position of the sun. If the geometry matches the direction of the shadow, I'd conclude that's what it is, though it seems highly unusual to see a shadow in air.

I've asked in the X thread for the date/time. I also suggested that if we identify the plane there's a chance we can get the flight crew to see the image, I believe a few are often happy to see images of their planes, especially doing something rare,

Is it even possible for the shadow to be that distinct yet that much narrower than the obect casting it?

Also, it looks like the shadow in the sky is not perfectly aligned with the contrail but slightly to camera left... in that case, shouldn't any shadow on the ground be well off to camera right?