Originally Posted by
moondog
On east bound flights, tail winds play a major role in route planning. As such, transpacs ex-PEK often trod along the (south side of the) NK/SK border before making a slight left to set up for one of the main oceanic paths.
In both directions, the routing often deviates pretty substantially from the ideal great circle, utilizing a much "flatter" routing, particularly eastbound. UA 1/2 provide pretty good indications of what SFO-BKK routing might look like.