I was just doing a bit of skywatching out of the train window when a dark trail caught my eye. At first I thought it must be a contrail shadow but there was no obvious source, and the sun angle seemed wrong. Then I noticed that it lined up with what looked to be a distrail in a cloud overhead. Here's a series of photos. You can see that it also seems to line up with a distrail in a cloud in the distance. Any ideas what's going on? There seems to be some thin hazy high cloud with a few faint ripples visible in it, so is it possible the distrail is continuing through the haze? That seems unlikely as the thin cloud is presumably much higher than the (stratocumulus?) cloud where the distrail appears overhead. The dark trail was only visible briefly so it seems to be dependent on sun angle, disappearing as the train moved on. Photos were taken 8.00-8.01pm this evening as the train was near Byfleet and New Haw station in Surrey, looking roughly west. Planes are landing at Heathrow in that direction and taking off to the east today.