Originally Posted by CPRich

Just looking at the last AC flight in each direction, you'll see the eastbound flight over the Pacific was flying at a groundspeed of 650-750mph for much of the flight. This indicates tailwinds of 90-190mph. Flying that same path in reverse, you'd only be moving at 370-460mph, resulting a 20+ hour flight (even if there was enough fuel). The flight over the pole westbound flew at 560-610mph.

The flight east over the Pacific was actually 1000+ miles longer, but the speed difference more than made up for the distance, making the trip 30 minutes faster.

http://flightaware.com/live/flight/A...455Z/CYYZ/VHHH

http://flightaware.com/live/flight/A...820Z/VHHH/CYYZ