Aviation Security

The alleged August 2006 terrorist plot to detonate liquid explosives onboard multiple commercial aircraft bound for the United States from the United Kingdom has highlighted both the continued importance of securing the civil aviation system and the potential that improvised explosive devices (IED) may be smuggled onboard passenger aircraft. The Transportation Security Administration (TSA) has primary responsibility for ensuring the security of civil aviation, which includes the safety of passengers and flight crew. One measure TSA uses to protect the aviation system is prohibiting individuals from carrying items that it determines to be a threat to the aircraft and its passengers into an airport sterile area or onboard an aircraft either in their carry-on bag or on their person. To implement this measure, TSA maintains a prohibited items list that informs both the Transportation Security Officers (TSO) who conduct passenger screening and the traveling public of items that will not be allowed into an airport sterile area or onboard an aircraft. In December 2005, TSA revised its prohibited items list to allow passengers to carry: (1) metal scissors with pointed tips and a blade 4 inches or less in length as measured from the fulcrum; and (2) tools--such as pliers, screwdrivers, and wrenches--7 inches or less in length (excluding crowbars, drills, hammers, and saws). TSA considers any incident that threatens the security or safety of an aircraft or its passengers and flight crew to be a security incident. These could include a range of activities onboard an aircraft such as disruptive passenger behavior, violence against a passenger or crew member, hijacking attempts, or the use of an improvised explosive device. By examining the security impacts of the change to the prohibited items list, this report considers the impacts that could result from a passenger attempting to use scissors or tools to hijack an aircraft or to commit other forms of violence onboard a flight. Such actions fall within TSA's statutory responsibility to ensure the safety and security of passengers and crew aboard aircraft. In accordance with Conference Report 109-699, which accompanied the fiscal year 2007 Department of Homeland Security (DHS) appropriations act, this report addresses the following questions: (1) What was TSA's basis for removing certain scissors and tools from the prohibited items list and what are stakeholder views on the change? (2) What have been the impacts, if any, of the removal of certain scissors and tools from the prohibited items list on the security of aircraft passengers and flight crew and on the effectiveness of checkpoint screening operations?

TSA's stated purpose in removing certain scissors and tools from the prohibited items list was to shift TSO focus from items considered by TSA to pose a low threat (including certain scissors and tools) to items considered to pose a high threat, such as explosives. The change also was intended to better allocate TSA resources to implement other security measures that target explosives--a change supported by the majority of aviation industry stakeholders that we interviewed. TSA's decision to remove these items from the prohibited items list was based on the professional judgment of TSA officials that these items do not pose a significant threat to the security of the cockpit or to passengers and flight crew as well as internal studies that sought to examine, among other things, risks to flight security and considerations of customer concerns and screening efficiencies. Based on our review of TSA security incident reports from the time period following the prohibited items list change (December 2005 through February 2007), there have been no reported security incidents onboard an aircraft involving the use of small scissors or tools. However, the impact of the prohibited items list change on security is uncertain because the absence of an event occurring involving the use of these items does not preclude the possibility that future occurrences could happen. In addition, with respect to the effectiveness of the change on checkpoint screening operations, it is not possible to determine this because the available data are inconclusive. As we reported in March 2007, TSA conducted informal studies 30, 60, and 90 days following the change and concluded that TSO time was freed up to focus on high-threat items, but our analysis of TSA data does not support this conclusion. TSA agrees that the agency could have conducted a more methodologically sound evaluation of the impact of the prohibited items list change, but continues to believe that the change nevertheless significantly contributed to the agency's efforts to free up TSO resources to focus on detecting high-threat items, such as explosives. It also is not clear whether the change had any impact on TSOs' ability to detect explosives--a key goal of the change. One way TSA measures the effectiveness of the passenger screening system in detecting threat items, such as explosives, is the results of threat image projection testing. However, TSA does not claim nor do the data definitively support that TSA's change to the prohibited items list had any impact on threat image projection results because TSA implemented other changes to checkpoint screening operations at or around the same time as the prohibited items list change. With regard to TSA's efforts to increase training for identifying explosives as part of its overall effort to become a more risk-based organization, TSA data between October 2004 and January 2007 show an increase in the average number of hours spent in training per TSO, but this trend began before the change to the prohibited items list and there are other factors that may have contributed to this increase.