Originally Posted by
swag
Why are there 2 circles? What do the different circles represent?
I'm assuming we don't know how exactly much fuel was on board the aircraft (but if someone does - please post it!), so the light circle is the distance we know it could have reached (it had to get to PEK, after all.) The shaded circle is probably a reasonable distance beyond the radius of PEK (since aircraft are loaded with extra contingency fuel in case of holds, weather, diversion, etc.)