The consistent growth of air traffic demand is causing the operational volumes at hub airports to approach their maximum capacities. With this growth, delays are increasing, and safety is becoming a more crucial problem. The terminal approaching and landing phases are especially important since the airspace is more crowded and operational procedures are more complicated compared with the en route phase. We have developed an agent-based stochastic simulation model which is useful to analyze the relationship among airport arrival capacity, delay, and safety. We first present a simplified queue model to demonstrate key ideas. Then, we give a detailed agent-based model that is calibrated to Hartsfield Atlanta International Airport. We use the model to evaluate several operational scenarios and examine the trade-offs between system capacity and safety.