An airbag apparatus for protecting an occupant of a vehicle comprises an inflatable chamber formed by at least one fabric panel and configured to be filled with an inflation gas and deploy into position to protect the occupant; and a tether connected to the panel to restrain deployment of the airbag. During the initial deployment sequence of the airbag, the tether fully extends to a first length. The tether unfolds in order to fully extend to a second length when a sufficient force is applied to the tether by the deploying airbag.