The National Airspace System (NAS) in the United States will become a complex array of commercial and general aviation aircraft, unmanned aircraft systems, reusable launch vehicles, rotorcraft, airports, air traffic control, weather services, and maintenance operations, among others. The Federal Aviation Administration (FAA) projects that by 2025 air traffic will increase by more than 50 percent with 1.1 billion passengers a year and more than 85,000 flights every 24 hours contributing to further delays and congestion in the sky. This increased system complexity necessitates the application of systematic safety risk analysis methods to understand and eliminate where possible, reduce, and/or mitigate risk factors. The product of this effort is the development of an Uninhabited Aerial System (UAS) safety analysis model (USAM). USAM is ground-breaking technology that combines research NASA has already conducted on future UAS flights and UAS performance profiles with technologies developed specifically for UAS flight risk analysis and NAS-wide simulation analysis. The combination of these technologies answers this important question by leveraging on existing work in creative ways and adapting it to the needs of the UAS aviation safety community.