Since the terrorist attacks on the United States in 2001, Congress expanded the workforce and mission of the Federal Air Marshal Service to help strengthen aviation security. In addition, the Service, as well as the Transportation Security Administration (TSA) was relocated under the Department of Homeland Security (DHS) and the Bureau of Immigration and Customs Enforcement (ICE). This report conducted by the U.S. General Accounting Office (GAO) examines operational and management control issues related to the Service’s expansion and considers the implications of the Service’s organizational realignment. Program data are analyzed, interviews are conducted, documentation is reviewed, and facilities are visited in order to address the following questions: (1) what procedures for obtaining background checks and providing training did the Service use to expedite the deployment of its expanded workforce; (2) to what extent has the Service developed management information and policies and procedures to support its expanded mission and workforce; and (3) what challenges is the Service likely to face as a result of its recent mergers into DHS and ICE. GAO findings include: (1) expedited procedures were used to obtain interim secret security clearances for air marshal candidates with abbreviated training; (2) incrementally revised and abbreviated its curriculum for training; and (3) the beginning stage of developing management information, policies, and procedures to support expanded workforce and mission. Challenges are likely for the Service in implementing changes, including changes to its roles, responsibilities, and training and to its procedures for coordinating with TSA’s security organizations.