Congestion problem in the airport declines the passengers' satisfaction. The passengers' satisfaction is an important matter to the sustainability operation of the airport. Airport management has to develop a company program to improve the quality of service to the passengers. To regulate the passengers' processes, it is important to define the performance of existing system. The objective of this research is to measure the performance the existing system of airport departure terminal and provide a suggestion to airport management of Soekarno-Hatta International Airport. Discrete-event simulation method was developed to measure the system. ProModel simulator software, from ProModel Corporation, was utilized to simulate the existing system of Departure Terminal in the Airport. To measure the performance, authors focus on some indicators i.e. passengers processing time, passengers waiting time, and utilization of each station.