An integral-equation-based, Full-Wave Layered Interconnect Simulator (UA-FWLIS) has recently been developed for the simulation of stripline interconnects. In this paper we extend UA-FWLIS so that it can handle apertures in the power/ground planes. Apertures are often cut in power/ground planes to help reduce the effects of the digital noise on the more sensitive analog circuitry. In order to account for the effects of the apertures, we use the field equivalence theorem to define equivalent magnetic currents that flow in the apertures. These magnetic currents interrupt the flow of the electrical currents on the power/ground planes, and they also allow for coupling between traces in adjacent layers in multi-layer stripline structures.