Great find OP, very well played.
Inspired, I had a go at mapping a couple of FPS black holes in the UK - one at EGNX which turned out to be too small to interpret properly really but was definitely the same kind of shape (right angle triangle with curved hypotenuse).
Then I found one further north which was larger…
There was an airport near the centre of the 30nm circle that fitted the arc nicely - but it was only a grass strip near Bridlington - hardly an international hub 
Not sure it adds much but thought I’d share