This report compares two models for vulnerability assessment for aircraft. The Swedish model does not develop or support numerous vulnerability/survivability computer programs. The vulnerability assessment community in the U.S. is many times larger then that of Sweden. The three largest differences between the mathematical models are structural kill (not treated in the Swedish model), the calculations of fragment penetration capability, and the definition and the use of damage criteria. As the structural kill is not treated in the Swedish model, this model is not capable of handling warheads specially designed to cause structural kill. Both countries have a need to make more sensitivity analyses of their models.