This paper discusses voltage collapse cases in a power system using static and dynamic approaches. The studies are conducted on a summer peak load planning case of major power system in the U.S. The power system has significant air conditioning load. A detailed load model based on measurement from actual recordings of power quality meters is used in time domain studies. The impact of modeling of air conditioning load is examined. Both static and dynamic approaches have been used for the analysis of voltage collapse. The application of modal analysis at the point of collapse to study the voltage collapse caused by high air conditioning load is discussed. The significance of the direction of power transfers while calculating the point of collapse to perform modal analysis is also discussed.