Explosives, given today’s technology, may appear in virtually any form: solid, liquid or gas; and be made to look like any innocuous object – from an IPod music player to a sports drink, baby bottle or prescription (even with a correct name on it). Screening for certain conventional explosives takes place at the airport security checkpoint, where passengers’ carry-on bags may be swabbed for explosive residue, at the ticket counter, where some checked baggage is screened using giant detection machines, in secure baggage areas, where bomb dogs sniff random bags for explosives and TSA screeners randomly open some passengers’ bags and inspect them, and using the “known shipper program,” which relies on branded shippers who use airliners, to vett some commercial cargo placed aboard the planes.
The ability of explicit bag screening, that is “bag-swabbing” technology, to detect conventional explosives is significant, approaching 100% against conventional explosives like dynamite and plastic explosives. In fact, it is usually the high “false positive rate” under which the system falters, closing airports for hours at a time, for what turns out to be an innocent object. But this is time-consuming and impractical in a system of our system’s size. At the checkpoint, only a small percentage of passengers’ bags are swabbed. Further, swabbing doesn’t address a passenger carrying explosives in their shoes, bra or other area.
Richard Reid, the infamous American Airlines shoebomber, wore explosive shoes through screening not once, but twice; both times successfully. The first time, he was stopped on suspicion, interrogated, and then released. The interrogators never inspected his shoes and he successfully boarded an airplane wearing them the following day.
There is virtually no technology of any kind that has a prayer of detecting liquid explosives, even though they have been used against airliners for almost twenty years; and, there is no technology that can detect explosives from a stand off distance, and/or with a low false-positive rate. Moreover, terrorists may be able to easily sneak completely innocuous liquids onboard (peroxide, nail polish, etc.) and manufacture explosives in an airliner’s lavatory, if no one is onboard trained to detect or to stop them.
Because of practicality, we rely, primarily, on the standard x-ray unit to visually look for potential explosives at airport checkpoints. X-ray units are designed to “see” metal. They are very poor at seeing plastics or liquids. In recent government tests, x-ray unit operators failed to detect hidden bomb-making materials 100% of the time – that’s right, they failed every time they tried!
At the ticket counters, machines the size of minivans have been purchased to analyze checked baggage for explosives. These machines cost millions of dollars a piece and are so heavy, in some cases the floor of the airport cannot hold them. While major airports have at least some of these machines, smaller airports do not. Obviously, a terrorist team will simply enter the system at a smaller airport, as one terrorist did in Roanoke, VA, in preparation for the 9/11 attacks.
Freight is also routinely loaded aboard commercial airliners by contract freight companies. The only “screening” applied to such freight is the “Known Shipper Program.” Basically, the freight company vouches for the shipper as safe. The program is only as good as the attendant shipper vetting procedures at the freight companies, who obviously have a revenue incentive to do business with as many shippers as possible. Since 9/11, there have been two incidents where individuals have “shipped themselves,” successfully stowing away on commercial cargo jets. Not only is this a failure of the cargo screening process, the individuals in question may have had direct access to the flight’s crew, since cargo jets sometimes do not have cockpit doors.
We must recognize, however, that, as terrible as an explosion of an airline would be, it does not present the far greater threat of an airplane commandeered and used as a weapon against a ground target like the World Trade Center. Multiple airplanes simultaneously exploding in a coordinated attack, though, would devastate the economy and the airline industry. This exact attack was planned by terrorists several years ago, before being foiled by the FBI, and was the model used in the summer of 2006, in London.
It is obvious that terrorists will continue to retry attack models, whether they have been successful in the past or not.
The reliability of our explosives detection system is 15%.