The air cargo challenge

Explosives hidden in air cargo pose the same threat to passengers as those hidden in baggage, but the methods of detection throw up more complex issues, says Rapsican SystemsWhen Pan American Flight 103 was destroyed over Lockerbie, Scotland, killing 259 passengers and crew and another 11 people on the ground on December 21, 1988 this tragic event revealed the vulnerability of commercial aircraft to acts of terrorism. After a lengthy investigation, the catastrophe was attributed to plastic explosive detonated in the cargo hold.

More recently, the September 11 attack on the United States reminded the world that aircraft can be used as terrorist weapons. To counter this terrorist threat, measures have been implemented principally focused on detecting weapons and explosives on airline passengers and in their baggage. To date, less has been done to apply a similar level of scrutiny to air cargo, which is also carried in the hold of passenger aircraft, as well as on designated cargo aircraft. Explosives hidden in air cargo pose the same threat to the flying public and those living under flight paths.  

Implementation of effective and efficient air cargo inspection is challenging for a number of reasons, including: Volume of air cargo; multiple stakeholders; time critical process; small threat quantity; variety of inspected objects. The US Transportation Security Administration has stated that: “100 per cent physical inspection of all cargo shipped on both passenger and cargo planes is not a viable alternative.” However, work is ongoing to improve the quality and quantity of air cargo inspection.

Volume of Air Cargo  
The 2005 estimated worldwide air cargo traffic is approximately 178 billion tonne-kilometers (RTKs) of goods transported. Total world air cargo averaged 5.1 per cent growth for the past ten years.

Multiple Stakeholders
While governments are mainly concerned about protecting life and property, businesses such as airports, airlines, shippers, and customers, are also interested in maintaining the flow of commerce essential to their time critical operations. The Air Transport Association estimates that air cargo generates $17 billion in annual revenues for US passenger airlines and all-cargo airlines. This accounts for over 100,000 US jobs. While inspection of 100 per cent of air cargo may be an admirable goal, its achievement will depend, largely on finding a solution that all stakeholders can agree on.

Time Critical Process
Cargo is typically shipped by air because its delivery is time critical. As a result, the effect of delays caused by inspecting air cargo is magnified. One approach is to implement air cargo inspection as much as possible within the existing cargo handling infrastructure and operations.

Small Threat Quantity
The amount of explosive that destroyed Pan Am Flight 103 was estimated at 300 to 400g, which illustrates the small size of an aviation threat quantity. The challenge is more difficult as the container in which the explosive is hidden becomes larger. Detecting a small quantity of explosive in an LD3 container, which holds many individual packages, is more challenging than detecting the same threat in an individual checked suitcase.  

Variety of Inspected Objects  
Air cargo containers come in a variety of shapes and sizes. To be most effective, a comprehensive air cargo inspection approach must accommodate the full range of container designs.

One way to inspect the greatest amount of cargo in the shortest time is to inspect trucks transporting cargo to the airport.However, the size of the truck and the number of objects it holds increases the challenge of detecting small threat quantities. In addition, suspicious packages detected by the inspection must be removed from the truck, which requires a time consuming and labour intensive unloading operation. At the other end of the spectrum is break bulk inspection, where each object is inspected individually. While this approach reduces the size of the inspected object, it maximises cargo handling and eliminates any efficiency achieved by inspecting multiple objects at one time. Between these two extremes is inspecting containers or pallets, which hold a number of objects. Because the containers and pallets are generally smaller than a truck, this approach achieves inspection efficiency without all of the drawbacks.  

Inspection Methods
Methods for detecting explosives and other threats in air cargo can be divided into two categories. The first is imaging; a radiation beam is used to create an image of the cargo in the inspected object. An inspector examines the image and identifies suspicious objects that may be associated with threats.  Radiographic systems, such as x-ray and gamma-ray scanners, are examples of imaging systems. Imaging systems can be used to detect the presence of threat objects that have definite shapes, such as firearms. However, they are not as well suited for detecting threats without defined shapes, such as plastic explosives.

The second method is automation. The inspection device examines the inspected object and automatically detects the presence of specified threat materials, such as explosives. Dogs that detect drugs and explosives are an example of an automated system. Neutron inspection systems also provide this capability. A beam of neutrons interacts with objects in the cargo and the response is analysed to identify threat materials, including explosives and chemical weapons.

Baggage and cargo inspection methods currently used at airports, seaports and border crossings form the basis for techniques that may meet the requirements of air cargo inspection. However, significant challenges exist to achieving routine air cargo inspection, let alone inspection of 100 per cent of cargo. These challenges include inspection technology and its practical application to a huge volume of air cargo, assuming that agreement can be reached among all of the relevant stakeholders.

Further information:
Rapiscan Systems
Phone: 0870 777 4301    
Fax: 0870 777 4302