This morning a large aerodynamic contrail formed near Shingle Springs, California. The contrail formed partially in a cloud layer, and with the low sun it created a significant dark shadow on one side, and maybe something of a distrail. The above photo also shows a younger contrail to the right of the middle, leaving a shadow on the cloud layer.
The photo session started when I saw this older contrail fragment, about where the large contrail meets the horizon. It had very sharp sundog colors.
Just after that, I saw this plane flying east:
Zooming in, you can see it's a twin engine plane with the engines mounted on the tail. It's leaving aerodynamic contrails from the wing surface, and not the engines.
This was at 7:03AM, PDT, so 14:03UTC, July 15, 2016. The plane is an MD-90-30, registration N919DN, flight DL2488 from San Jose to Minneapolis. It had just finished climbing at that point, and most of the contrail was the plane cruising at 29,000 feet.
I'd set up a timelapse earlier, hoping to catch a sundog in another contrail fragment that was moving towards a position where I'd see the other one. And this showed a large part of the formation and evolution of the contrail.
I also took some nice HDR images, at this point the contrail looked quite dramatic, as only the portion that was in the cloud layer had persisted, and this almost started to look like a tornado.
There were also nice corona colors around the sun for the entire time. I took this at 6:57AM, before the plane arrived.
In this last shot the contrail just visible in the bottom right, but has largely merged with the cloud layer. This was taken at 7:40, or about 35 minutes after that segment had formed. Notice there are still corona colors around the sun.