“As we handle more operations and passengers in the air, we must make certain we have the capacity to handle increased traffic on the ground.”- Jane Garvey, FAA Administrator (4/20/98)The FAA Technical Center (Aviation System Analysis and Modeling Branch, ACT-520) has been responsive to the FAA Airport Capacity Program customers for the past 22 years, developing, testing, and applying airfield and airspace simulation models. More than 90 capacity studies have been completed with ACT-520 personnel contributing their technical expertise to the Airport Design Teams. The teams are comprised of FAA personnel, airport operators, air carriers, other airport users and aviation industry representatives at major airports throughout the US.Initial studies focused on modeling airport operations from final approach, taxi, gate operations and departure processing. Later in the program, local airspace studies were included in some airport study efforts. Both airport and airspace studies include either a full scale design team study or a less detailed tactical initiative. Recently, National Airspace System (NAS) modeling personnel joined the group providing system modeling expertise in the NAS Architecture and Flight 2000 programs.An arsenal of analysis tools and computer simulation programs has been developed and tested to accomplish each task. The group has experience using the models they have developed or improved upon (ADSIM, RDSIM, RQSIM, etc.), have obtained from other FAA entities (SIMMOD, NASPAC, RAAM, etc.) and have acquired under contract or agreements (The Airport Machine, TAAM, MIT Delays Model, etc.). This modeling capability permitted the group to perform simulations of improvements in the categories of airfield, facilities and equipment, ATC operational, and airport policy improvements. The delay effects of aircraft demand (schedules), fleet mix, runway configurations, weather, aircraft separation standards, etc., were measured in the studies.Future studies will require new model development particularly in the arena of system wide impacts measured on an annual basis. The requirement for an analyst to know both the model inputs and the working of the model's code will continue to apply for a successful study. As in the past, no universal model will answer every question and existing models will require enhancements to reflect unique requirements. Because of the increases in computing speed and memory, the fidelity of simulations can be enhanced in the near future through new hardware acquisitions.ACT 520's past participation in this enterprise has generated an understanding of the interrelationships of various airport and airline systems. Our seven senior analysts and eight junior analysts combined with their professional expertise are ready to address the FAA Administrator's concerns about capacity.