The Aurora Borealis, "Dancing Curtain" , is occasionally visible flying to AMS from U.S. West Coast. Good to be on left side for it. On the return, the right side is nice, as it is a day flight in the Arctic Circle, and the Northwest Territories is great for taking photos. On our Dec return, we left quite late (1:00 pm) and took a very northerly route; the sun often dipped below the cloudy horizon 'til we turned hard left. Saw some spectacular ice flows.