A method and system for modeling an inflatable supplemental restraint device for a vehicle includes operating a simulation system according to a first step in which the restraint device is modeled in a fully inflated configuration using a finite element model. The modeled airbag is then deflated and flattened. The flattened airbag is subjected to simulated folding using a finite element model. Inputs drawn from the results of successive portions of the simulation are used in the later modeling steps.