This paper describes a half car model of an active suspension where control strategy is based on controlling the mass flow rate of air into the air spring. Three control strategies based on controlling the mass flow rate of air into air spring are presented. Equations of motion are developed and solved using MATLAB. Using the results of the simulation of the model based on each of these control strategies for different gain values in the control system, it is concluded that the stiffness of the suspension can be dynamically controlled by using a suitable value of gain in the control system. It is observed that an undamped active air suspension based on mass flow control having the mass flow of air into air spring as a function of the relative velocity between the sprung and unsprung mass with the gain equal to one has zero response of the sprung mass in bounce. The response of sprung mass in bounce and pitching motion is less than the input from the road for the damping ratio in suspension not exceeding 0.3. Hence, the control strategy based on mass flow control having the mass flow of air to air spring as a function of the velocity of sprung mass with respect to the velocity of unsprung mass with the gain equal to one is proposed.