>>2794937>that massive empty space in Western China>Why?that's the Tibetan Plateau
and multiple reasons
Chinese airspace is... quite interesting in itself
>only allow flying on narrow corridorsthe majority of airspace is reserved for government / military use
which makes for some really weirdly shaped, longer and more busy routes
but it's also dangerous flying over the Himalaya
in case of an depressurization event, airplanes need to fly down to ~3km
but the tibetan plateau has an average height of ~4,5km
which makes this impossible
also generally less room / time for error
if you have to glide or anything else happens with your turbines
you're awfully close to the mountain tops
the other technical reason
are weird upward wind currents
ranging from mild annoyance / turbulence to passenger getting thrown around
also suitable emergency airports are far away
typical ETOPS would allow it
but again, increased floor height to ~4,5km makes it more dangerous