Longest 'direct' flight from China ?
 

Ok, CA907 - Beijing (PEK) to Sao Paulo Brazil (GRU ).
-CA or Air China flies this twice a week, day 4 & 7. 10,923 miles, 23 hours, plus a 2 hour stop in madrid for fuel.

Any longer "direct" flights from China ? , Has to be the same flight #

Remarkably not far off the GC route.

http://www.gcmap.com/mapui?P=pek-gru,+pek-mad,+mad-gru

Since a non-stop flight IS a direct flight, SA doing the run between JNB and PEK counts.

So, what's the shortest flight from the US to China?

As far as I can tell from a cursory search,

Scheduled = HNL-PVG on MU (4,926 mi)

Charter = SPN-PVG on 3U (1,872 mi)

If you're talking "mainland to mainland" flights it would be SEA-PEK.