Ahhhh....very interesting. Makes sense. Without the ability to fly polar, which involves flying through Chinese airspace, they'd have to come down over the North Pacific and Japan, and with the massive headwinds the flight couldn't make it nonstop.

On the return they can fly the same routing, but no problem with the tailwind.

On the 3 or 4 HKG->NYC nonstops I've flown, I think only one time did we take the polar route, even though the North Pacific routing adds about 1,000 miles.