What is air resistance? Air resistance, also called drag, is the forces that are in opposition to the relative motion of an object through the air. Drag forces act opposite to the oncoming flow velocity. Drag, unlike other resistive forces, depends directly on velocity. Drag is the component of the net aerodynamic force acting opposite to the direction of the movement and the forces working perpendicular are called lift. Drag is overcome by thrust. In astrodynamics, atmospheric drag is both a positive and a negative force depending on the situation. It is a drain on fuel and efficiency during lift-off and a fuel savings when a spacecraft is returning from to Earth.