The complexity and interdependence of operations on the airport surface motivate the need for a comprehensive and detailed, yet flexible and validated analysis and modeling capability. This modeling and analysis can be used to identify the most beneficial areas of research for the Next Generation Air Transportation System (NGATS) -ATM Airportal Project. It is essential, therefore, that the modeling approach properly considers all operational activities and possible capacity constraints in the entire airport surface and terminal operation as a complete system. To accurately model airport surface operations with detail and accuracy, we propose that it is necessary to consider techniques and strategies used to determine the flight's taxi route, and to determine the sequence to be used whenever two or more flights have contention for a taxiway or runway resource. This proposed effort will produce tools to support fundamental research of the concept and requirements for airportal operations in the NGATS by providing microscopic airportal surface modeling components that provide higher fidelity and greater validity of modeling than previously available. Through this effort we will also enhance the Surface Operations Data Analysis and Adaptation tool to provide the analysis capabilities required to support this microscopic airport surface model.