Another important aspect of dynamic pressure is that, as dimensional analysis shows, the aerodynamic stress (i.e. stress within a structure subject to aerodynamic forces) experienced by an aircraft travelling at speed v {\displaystyle v} is proportional to the air density and square of v {\displaystyle v} , i.e. proportional to q {\displaystyle q} . Therefore, by looking at the variation of q {\displaystyle q} during flight, it is possible to determine how the stress will vary and in particular when it will reach its maximum value. The point of maximum aerodynamic load is often referred to as max Q and it is a critical parameter in many applications, such as during spacecraft launch.