On a Christmas holiday flight on Turkish Airlines (TK1980) from Heathrow (1427 UTC on 22 Dec 2007) to Istanbul (1748 UTC) we encountered severe pollution over western Europe, illustrated here. As we penetrated altitude 10 km on climbing out of Heathrow it became apparent that the atmosphere was full of aircraft exhaust products, coloured brown. A passing aircraft was seen to leave a black trail. The density of the effluent appeared very great, such as to require relatively long infrared wavelength for adequate monitoring by satellite radiometry. Evidently the weather at this altitude was calm, and we were in an area of heavy air traffic. The stereo-pair below was taken at altitude very roughly 5000 m at 1440 UTC over East Anglia. Note that there were three (or more) distinct strata of clouds. The next photo was taken from cruising altitude about 11.5 km at 1519 UTC looking NE. It shows the brown colour of the layer near flight level above patchy low-lying fog over the surface of western Germany, with the Turkish Airlines logo and the moon above. The second photo, at 1636 UTC over southeastern Germany, was taken as late as possible before nightfall, and brings out the layer of pollution, of thickness perhaps a few hundred metres. [Reflections from inside the aircraft (at right) should be ignored.] There were few clouds in the lower troposphere. While very obvious at flight level, the layer of effluent would probably not have been apparent from the ground.

Returning to Heathrow on 5 Jan 2008, brown layers were again seen, but were much less massive.