The Small Aircraft Transportation System, or SATS, is a NASA-led initiative that seeks to revolutionize commercial air travel by increasing accessibility and mobility for the general consumer. The hallmark of SATS is on-demand, point-to-point air transportation from one of the nation's 5,400 public use airports and landing facilities. A second-order benefit is that it may help relieve congestion on the nation's highways and at our mid- to large size airport hubs. In 1999, NASA initiated a five-year, $69 million research program to study the feasibility and viability of SATS including development of the emerging technologies necessary to make SATS a reality. The five-year plan culminated in June 2005 in Danville, VA with a highly publicized flight demonstration and exposition serving as the SATS proof of concept. The "Highways-in-the-Sky" (HITS) premise inherent to SATS is arguably its biggest enabler, and it depends heavily on the idea of free flight. HITS will potentially be the first step in moving from traditional cars and other vehicles that travel on the ground to ones that will operate largely, if not entirely, in the air. The notion of "cars" that fly was first introduced by the entertainment industry in movies and television programs decades ago. But if mankind is ever to achieve that vision, we must have a start point. This research focuses not on the economic viability of SATS but rather on the degree of flight safety inherent to a program such as this. One can easily see how the introduction of a large number of autonomous vehicles operating simultaneously in an already dense region such as the National Airspace System might carry some degree of risk. This research introduces a modeling and simulation framework that will have applications to SATS at such time as the program must be evaluated from a safety of flight perspective. That will invariably include a high degree of simulation. This work also represents the first large-scale simulation focused primarily on how SATS will perform in the out-years.