To provide a flight system which properly responds to changes of wind directions and stably travels despite no wind, headwind or following wind.

The flight system 1 includes a body 3 with an air sac 7 and can stably travel despite wind directions by changing air resistance of a forward air resistance changing unit 9 which lies anterior in a traveling direction and controlled by a control system 5 to change air resistance and a backward air resistance changing unit 11 which lies posterior and controlled to change air resistance. The flight system 1 further includes a wing 13 which is vertically (perpendicularly) installed, and obtains a driving force by vertical wind generated by changes of altitude using the air sac 7 without using mobile power from a gasoline engine or the like. Further, the flight system can select the route toward the destination based on the prediction of changes of winds by a prediction system 6.