A systems engineering methodology was used to study the National Aero- nautics and Space Administration’s (NASA’s) Small Aircraft Trans- portation System (SATS) concept as a feasible mode of transportation. The proposed approach employs a multistep intercity transportation planning process executed inside a Systems Dynamics model. Doing so permits a better understanding of SATS impacts to society over time. The approach is viewed as an extension to traditional intercity transport models through the introduction of explicit demand–supply causal links of the proposed SATS over the complete life cycle of the program. The modeling framework discussed is currently being used by the Virginia SATS Alliance to quantify possible impacts of the SATS program for NASA’s Langley Research Center. There is discussion of some of the modeling efforts carried out so far and of some of the transportation modeling challenges facing the SATS program ahead. Barring the effects of September 11, 2001, and the Persian Gulf War in 1991, the demand for air transportation services has followed a pos- itive upward trend in the United States from the 1980s to 2001. According to FAA statistics, air carrier and regional commuter oper- ations grew 4.1% from 1992 to 1998 (1). Some large airports like Hartsfield International in Atlanta, Georgia, handled more than 900,000 aircraft operations and 37 million enplanements in the year 2000. The percentage of passengers enplaned at the top 50 airports increased from 77% in 1989 to 83% in 1999 (2), indicating further consolidation of the airline hub-and-spoke system. There are signifi- cant indications that the capacity of the National Airspace System (NAS) is reaching a plateau owing to limited airport and airspace capacities. A natural effect of the NAS capacity constraints on travel is increased travel times for random origin–destination (O-D) pairs due to circuitous routing caused by the mature hub-and-spoke air transportation network. These trends promote travel inefficiencies (as measured by door-to-destination travel times) that have prompted the National Aeronautics and Space Administration (NASA) to exam- ine new aeronautical technologies to reverse the pattern. One pro- posed set of technologies is the Small Aircraft Transportation System (SATS). According to NASA, the SATS promises affordable air transportation to the public, using inexpensive all-weather aircraft— privately owned, rental, air taxi, or some form of fractional ownership. The SATS is a spin-off of the aeronautical engineering advances made by NASA and industry in the past 6 years. NASA created the Advanced General Aviation Technology Experiment (AGATE) pro- gram to improve the aerodynamic and systems design features of light aircraft and to study new manufacturing methods for General Avi- ation (GA) aircraft. The General Aviation Propulsion program developed propulsion technologies to complement the products of AGATE. One of the arguments supporting the SATS concept is the potential use of several thousand public airports without commercial revenue service in the United States. If the affordability and safety- related technology challenges are resolved, this form of transporta- tion could allow access to many rural and urban communities alike. It is important to recognize that the SATS is a concept that faces numerous challenges, including mode affordability, environmental and energy impacts, airport infrastructure, air traffic integration, soci- etal acceptance, human factors, flight safety, and so forth. Neverthe- less, it is interesting to remember that many of the same challenges burdened the development of the automobile 100 years ago. The most pressing research need for novel transportation concepts like the SATS is the development of a coherent system architecture definition, including the potential end state for the system, and a sys- tems engineering approach to prove that the concept works. This paper describes an integrated approach to study the SATS that is a first iteration to achieve this goal. SYSTEMS ENGINEERING APPROACH TO STUDY SATS System engineering methodologies have been developed and imple- mented in the analysis of large-scale systems over the past 5 decades (3). These methodologies are commonly used in defense and aero- space programs and in technology-based systems, such as comput- ers and communications systems. Intercity transportation systems such as the SATS involve many of the same challenges, to reach acceptable planning and design solutions. The initial step common to the initiation of major new systems is the development of a system architecture. A system architecture is the framework that describes how the system components are interfaced and work together to achieve total system goals. It describes the operation of the system, what each component of the system does, and what information is exchanged among the components. Systems Engineering Viewpoint Any transportation system intended to serve society through the 21st century and beyond must address a hierarchy of goals and issues rang- ing from the strategic (sustainable development) to the tactical (the concept of operations), and it must include interfacing with the exist- ing transportation system. In many past studies, transportation plan- ning, policy, investment, and operating decisions for one mode have been made in isolation from those in other modes—incomplete inputs from a broad base of disciplines. An integrated approach is thus Integrated Model for Studying Small Aircraft Transportation System Antonio A. Trani, Hojong Baik, Howard Swingle, and Senanu Ashiabor 201 Patton Hall, via Department of Civil and Environmental Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061. Transportation Research Record 1850 ■ 1 Paper No. 03-4336