A restraint system is provided for helping to protect an occupant in a seat of a vehicle and includes an airbag having a main portion inflatable from a stored condition to a deployed condition in front of the occupant. Arms extend from the main portion and are spaced apart from one another to form an uninflated volume for receiving the occupant in response to a vehicle collision. The arms are configured to inflate to opposite sides of the occupant prior to occupant penetration into the airbag.