[mxfh]

This is not far north because of winds, it's just the shortest line!

Great circle distance (Curves in Mercator, straight lines on globe) vs. Rhumb lines (Straight in Mercator, constant course angle against meridians)

http://demonstrations.wolfram.com/ComparingLoxodromesAndGrea...

[edit] added picture for explanation

http://i.imgur.com/wJS0ry1.png

Lines of same color have identical course

[cs02rm0]

Sort of, journeys in the other direction are pushed even further north (or, actually north of the straight line) though which I believe is because of the winds. - i.e. it's a factor, isn't it?

[mxfh]

Jet Streams are a factor but their position varies.

The appearance as a northbound curve is the effect of the straight Orthodrome/Great Circle line projected into Mercator.

http://en.wikipedia.org/wiki/Transatlantic_flight#Transatlan...

[edit] I think it's fair to assume the winds are relatively stable and more intense further north so eastbound (US > Europe) flights might deviate even further to the north.

http://en.wikipedia.org/wiki/North_Atlantic_Tracks#Route_Pla...

http://earth.nullschool.net/#current/wind/isobaric/10hPa/ove...