Following the September 11th terrorist attacks in the United States, the FAA issued flight restrictions to prevent planes from flying over certain areas, including stadiums. This action was taken to protect the public from further terrorist attacks involving aircraft as weapons. In December 2001, the FAA and the TSA began waiving flight restrictions to allow certain pilots and aircraft to fly near stadiums. However, in February 2003, Congress passed legislation that suspended the waiver process and prevented aerial advertising pilots from flying near stadiums for 1 year. In January 2004, Congress continued this restriction indefinitely. This letter was written in the event that the restriction on waivers for aerial advertising flights stadiums is repealed. The threat assessment to stadiums is reviewed and confirmation is sought to ensure that action is taken to address vulnerabilities and inefficiencies in the background check process for aerial advertisers. FAA and TSA regulations, policies, procedures, and documents relevant to waivers of flight restrictions were assessed, as were a sample of 100 waivers for aerial advertising pilots approved by FAA and TSA. Additionally, interviews were conducted with responsible FAA and TSA officials. The results indicated that aerial advertising aircraft do not pose a significant threat, but a variety of factors make general aviation vulnerable to terrorist attacks. These factors, coupled with the ability of terrorist organization to adopt creative methods of attack, underscore the need for security of all operations using general aviation aircraft and airports, including aerial advertisers. Factors were also identified that could limit the effectiveness of background checks, such as inconsistencies in information collection. In the event that waiver restrictions are repealed, TSA should determine whether more comprehensive background checks are warranted. After reviewing the full report, FAA and TSA officials generally agreed with the information contained in the report and with the recommendations for improvement. Figure