My office window, several floors up, near to Heathrow, facing westward, gives a nice view on clear summer contrailing evenings of westbounds, often to them being over the Brecon Beacons. What was that about extreme air pollution ?
In the reverse, one evening on Glasgow to London, overhead Blackburn, the lights of Hull were visible on one side and, crossing the aisle, of Dublin on the other. And I've commented here before that on Glasgow to London City, the descent track is so convoluted nowadays that France is regularly visible on the left.