The enemies of the United States still view the U.S. aviation sector as a highly-attractive target, as evidenced by several thwarted plots and attempted attacks. In addition to the threats posted by al-Qaeda and its affiliates, the thousands of foreign fighters, including U.S. citizens affiliated with terrorist groups like ISIS, are a growing and serious threat to the security of U.S. aviation and the homeland. TSA relies on a multi-layered approach to aviation security, with everything from Federal air marshals to canines to the latest explosive detection technology. One of the these layers is a behind-the-scenes program known as Secure Flight. This program takes passenger data it receives from airlines and matches it against the U.S. Government's consolidated terrorist watch lists, including the No-Fly and Selectee lists. This program is crucial, not only for domestic flights, but also for protecting the international flights bound for the United States.