Radar cross section (RCS) and far field predictions of an aircraft is an important topic in computational electromagnetic. It requires large computational resource since it is usually electrically large. GEMS uses a cluster with a distributed memory to simulate this type of problems and can generate an accurate result in a reasonable time frame. For example, we apply GEMS to simulate an aircraft that is discretized into 823x1000x296 non-uniform cells using 91 processors of GEMS HPCC system, and it took 20 hours for 25,000 time steps. A plane wave is coming from the φ=270 degree and θ=90 degree