The strong growth of air traffic demand in the Asia-Pacific region is expected to continue, and it will be necessary for Japan to increase capacity in the area of the North Pacific over which it has responsibility for Air Traffic Control. For such measures, the influence of wind on the most efficient operating routes must be considered, but the westerly jet stream varies during the year so it is difficult to consider its influence comprehensively. Currently, flexible route operations that consider winds aloft wind are implemented in the North Pacific oceanic area, and track information is published daily. This paper provides the result of trend analysis and classification of flexible routes in the North Pacific in preparation for a future efficient route study of the area. Published flexible route data for one year were analyzed, and k-means clustering was used for classification of the large volume of data. As a result, although the variation of tracks over a year was found to be large, classification showed a north-south trend: In the summer, when the westerly jet stream is relatively weak, a trend to take routes close to the Great Circle on its north side was indicated, whereas in the winter, when the jet stream is strong, routes tend to be south of the Great Circle.