To enhance aviation security, the Department of Homeland Security's (DHS) Transportation Security Administration (TSA) developed a program-known as Secure Flight-to assume from air carriers the function of matching passenger information against terrorist watch-list records. In accordance with a mandate in the Department of Homeland Security Appropriations Act, 2008, GAO's objective was to assess the extent to which TSA met the requirements of 10 statutory conditions related to the development of the Secure Flight program. GAO is required to review the program until all 10 conditions are met. In September 2008, DHS certified that it had satisfied all 10 conditions. To address this objective, GAO (1) identified key activities related to each of the 10 conditions; (2) identified federal guidance and best practices that are relevant to successfully meeting each condition; (3) analyzed whether TSA had demonstrated, through program documentation and oral explanation, that the guidance was followed and best practices were met; and (4) assessed the risks associated with not fully following applicable guidance and meeting best practices.