Why are different routes flown between the the same pair of airports? On two of my trips (same airline, same kind of plane 777), I noticed that the airplane took very different routes (from New York to UAE).

1st Trip in 2012 (blue): Duration 11h 30m

2nd Trip in 2013 (green): Duration 13h 00m

I know that the blue line is the shorter distance, and probably also because of jet streams, it took lesser time. But why a plane would take this green route, even not considering jet streams?

Since I am not an important person, I could not ask the captain of the plane this question at the end of journey.

P.S.: I observed the flight paths on the entertainment system this airline has for all passengers.
Lots of reasons are possible, ranging from winds to other issues. In this case I'm willing to bet that the first flight was based on the most efficient routing to take advantage of tailwinds en route and that the second was avoiding Syrian and Turkish air space because of the political issues there earlier this year.

See also:


Flight Delays Incurred Avoiding Syrian Airspace
Royal Jordanian stops flying over Syrian airspace