Flight Paths - Visualized

Alexey Papulovskiy shows us how its done - collecting data from planefinder.net in October and charting it.  The results are remarkably cool - as the image above of the London regions shows.
As he puts it

Turns out, besides Flight Levels (FL) (which are indicated on my map by dots’ color: red ones stand for lower altitudes and blue — for higher) planes have pretty specific “roads” and “highways” as well as “intersections” and “junctions”. You can see this for yourself by taking a look at the Russian part of the map: it’s less “crowded”, so the picture is as clear as it gets. The sky above Moscow area looks particularly interesting: civil flights are allowed there only since March 2013 and only with an altitude of 27.000 ft or higher

Go to the site for an interactive version - its worth the time