With increasing numbers of international flights and air travelers arriving in the US annually, the rapid spread of communicable diseases has grown. Epidemics of novel infectious diseases have emerged and rapidly spread globally in association with air travel, including the severe acute respiratory syndrome (SARS) outbreak in 2003 and H1N1 in 2009. In order to anticipate and mitigate the consequences of future rapid disease spread, the MITRE Corporation, in collaboration with the (US) Centers for Disease Control and Prevention, developed a risk assessment tool using a Susceptible-Exposed-Infectious-Recovered model and detailed flight and population data. The emergence and spread of prototypic pandemic influenza was simulated based on a theoretical geographical point of origin and its communicability. More than 50 international metropolitan areas were analyzed as potential points of origin to simulate the rapidity of spread to the US. The basic reproduction number (Ro), defined as the average number of persons to whom one infected individual transmits disease in an immune naive population, was varied from 1.4 to 1.9. The starting numbers of infectious persons at each origin also were varied (100 or 500 persons, 5% infectious may travel). Waves were computed as aggregate across metropolitan areas modeled in the US. The visualization of the first pandemic wave was most apparent in simulations of Ro = 1.9, resulting from 500 infectious persons at each origin. More than 50% of origins indicated that aggregate waves peaked around Day 125, while 30% of origins peaked around Day 90. Additionally, the time, in days, from its origin in six continents into the US was compared, and a two-week delay was found from South America compared with other continents. This simulation tool better equips policy makers and public health officials to quickly assess risk and leverage resources efficiently via targeted and scalable border mitigation measures during a rapid global outbreak.