Just looks like a contrail from a plane heading away from the camera. At the end there is another trail from a plane travelling from right to left,
which is the exact same colour and contrast. I'm no expert though.
It's clearly a contrail from an airplane heading away from the camera. The color is due to the risng/setting sun (not sure what time of day this
was). Since the sun is low to the horizon, objects higher up in the atmosphere are the only things getting hit by rays of sunlight.