The Transportation Security Administration (TSA) staffs and operates over 450 airports in the US. TSA has been using simulation to determine staffing requirements since 2005 and has recently completed a refresh of their manpower planning and scheduling system. The objectives of the effort were to replace the GPSS simulation engine, optimizer and user-interface (UI) to take advantage of current network-based systems technologies. The previous system was distributed to the 200+ users as a stand alone application. This presented maintenance, security and performance issues, especially during the annual budgeting process. This paper focuses on the creation and integration of the simulation engine which was required to replicate and improve on the existing GPSS model accuracy and performance. Additional considerations included providing TSA an easy-to-use simulation platform to maintain the simulation engine, make model and data edits and expand the use of simulation technology within TSA.