Well, that was a nice birthday treat…just seen a DHL flight that seemed to be almost overhead, but was actually over Cambourne about 12 miles away. According to the Plane Finder flight tracker it is travelling from Brussels to Miami at an altitude of about 7 miles at 360 knots, so not delivering my presents. The vapour trail did not persist for long, dissipating within ten minutes or so.
The above is a cropped photo taken with a 600mm zoom on a 2/3-frame camera (zoom equivalent to 900mm, digital crop to 1800mm). Odd the perspective one has looking at the jet flying over. It seems so high, but it’s not as high (7 miles) as it is far away (12 miles) if one were to travel from here to the town over which it was flying when I took the photo. So camera to aeroplane distance is about 14 miles, using Pythagoras.
As I finish writing this post I can see the pilot has changed heading slightly and has just flown over the Lake District.