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Glasssos 
Originally Posted by
Glassos
The polar route is always shorter time (and distance)wise going West. The return (eastbound) trip may be shorter time-wise, on a non-polar routing, due to the strong prevailing winds out of the west, particularly in the winter.
Asia to US generally doesn't go polar. US to Asia sometimes does, but not always. LAX to SIN nonstop on SQ stays at low latitudes. EWR to SIN nonstop sometimes takes polar route and sometimes across Atlantic, Europe and Asia.