America's Airports: The Threat From Within, House Homeland Security Committee Majority Staff Report [open pdf - 3MB]
"Approximately 900,000 people work at these airports, and many are able to bypass traditional screening requirements that travelers visiting the airports must endure. While the overwhelming majority of these airport workers take the inherent responsibility seriously, there are increasing concerns that insider threats to aviation security are on the rise. Recent insider threat examples discussed in this report include an attempt to detonate a bomb at an airport, gun and drug smuggling, an expressed willingness to smuggle explosives as well as employees who became involved in terrorist activities overseas. In all of these instances, the employees in question had access to secure areas of the airport. These insider threats, and the lack of adequate access controls at airports nationwide, are of particular concern given the rise of terrorist groups bent on penetrating U.S. airport security to commit terrorist acts and 'lone wolf' attacks being inspired by terrorist groups like ISIS [Islamic State of Iraq and Syria."
United States Congress House Committee on Homeland Security: https://homeland.house.gov/