The intimate relationship between the local speed of sound of a flight environment and the lift and/or drag on a vehicle is discussed. The fact that this parameter will become increasingly significant as the speed increases is pointed out. In addition, it is noted that the usual source of flight “bumpiness” (i.e., wind variations) tends to become less effective as the speed increases. Examples of the sonic gradients which have thus far been observed in the high altitude regions of the earth's atmosphere are presented, and the circumstances under which such gradients would be most elective in perturbing a particular flight path are described. It is concluded that the variable vehicle loads imposed by atmospheric structure are composed of flow and thermo-dynamic components, and that both of these atmospheric parameters must be studied in the light of our expanding speeds and spatial activities.