An airbag cushion is disclosed for use in automotive protective systems. The airbag cushion includes a vent that, prior to cushion deployment, extends from the cushion exterior. A tether is coupled to the vent and to an interior surface of the cushion. Upon airbag deployment, the tether extends until taut or extends until the cushion encounters an obstruction. If pulled taut, the tether pulls the vent into the cushion interior where the interior air pressure effectively closes the vent. If the cushion encounters an obstruction, the tether remains lax, and the vent remains on the cushion exterior. Structures are provided for retaining the vent in the closed position during occupant ride down.