"The air cargo system is a complex, multi-faceted network that handles a vast amount of freight, packages, and mail carried aboard passenger and all-cargo aircraft. The air cargo system is vulnerable to several security threats including potential plots to place explosives aboard aircraft; illegal shipments of hazardous materials; criminal activities such as smuggling and theft; and potential hijackings and sabotage by persons with access to aircraft. Several procedural and technology initiative to enhance air cargo security and deter terrorist and criminal threats have been put in place or are under consideration. Procedural initiatives include industry-wide consolidation of the 'known shipper' program; increased cargo inspections; increased physical security of air cargo facilities; increased oversight of air cargo operations; security training for cargo workers; and stricter controls over access to cargo aircraft and air cargo operations areas. Technology being considered to improve air cargo security includes tamper-resistant and tamper-evident packaging and containers; explosive detection systems (EDS) and other cargo screening technologies; blast-resistant cargo containers and aircraft hardening; and biometric systems for worker identification and access control. […] In practice, the Transportation Security Administration (TSA) has relied heavily on 'known shipper' protocols to prevent shipments of cargo from unknown sources on passenger aircraft. ATSA also mandated that a security plan for all-cargo operations was to be put in place as soon as possible, but aviation security initiatives in the aftermath of the 9/11 attacks have primarily focused on passenger operations and full implementation of the air cargo strategic plan has not been fully completed."
CRS Report for Congress, RL32022