Why is the flight route going back to Vancouver different than it was going to Istanbul?

2017-07-17 11:29:36

I was on a flight (can't remember its number) from Vancouver to Istanbul, and this was the route (as described by Hudson who was with me)

We took off from YVR, headed north-east into Northern Alberta, then eventually over northern Saskatchewan and Nunavoot, then over Hudson Bay, the northern islands of Canada, Greenland, then the Atlantic, Norway, Sweden, headed south-east through Denmark, touched the edge of Russia a bit and then kept going south until we landed in Istanbul.

On the way back however, we went from Istanbul heading northeast until we reached Russia, headed east-north east, went pretty close to the pole, then went south east over the eastern part of the Aleutian Islands, then we bore south-east towards the B.C. coast, then we turned strait south into Vancouver.

Why is there such a variation in the route on the return journey? what factors played into this?

note that I described as best I could based on her description of our route because I am blind, an