First and second panels of air bag material are secured to one another with at least one seam defining a portion of a perimeter of a cavity bounded by the first and second panels, which is open along at least one unseamed portion extending along the first and second panels between endpoints of at least one seam. An opening in the second panel receives an end portion of an air bag inflator. Inflation gas generated by the air bag inflator is discharged into the air bag through the at least one unseamed portion, at least one of which is oriented downwards when installed in a vehicle. An air bag module cover incorporates first and second laterally opening door portions and a lower downward opening door portion that provide for a downward and outward initial deployment of the air bag.