Originally Posted by
nystateofmind
My parents, who are both US citizens, were denied boarding on a EWR-PVG flight connecting to I believe SIN or some other destination in Southeast Asia because they did not have the appropriate paperwork for China even though they were just changing flights and they had the tickets to prove it
This sounds like an example of airline (UA????) agents not knowing or applying the rules properly. To see what the rules are, look at the TWOV threads and wiki in the China forum on FT or, more officially, check TIMATIC. You need receipts for the next confirmed flight leaving China, which must be to a third country.
I've done the 72 hour TWOV at Shanghai, arriving on the DL flight from NRT and departing via the nonstop PVG-DTW about 68 hours later.
HOWEVER, if someone is ethnically Chinese, was born in China, or has ever had (dual) citizenship with China, then the rules are much more complicated.