The Price of Airline Security

On August 11, we received the unwelcome news that terrorists were planning yet another attack, this one involving US-bound flights from Britain that were targeted for demolition with liquid explosives. Fortunately, authorities rounded up many of the alleged plotters before they could do any damage, but the effects of their plans were felt immediately by thousands of would-be airline passengers whose flights were cancelled or missed because of tightened security checks. The problem of airline security is an interesting one from an engineering ethics point of view, because it brings to the surface matters of safety and expense that otherwise get little attention.

Air travel has not always been a relatively safe way to get from A to B. The primitive state of aviation technology in the 1920s meant that the few commercial passengers who flew back then were undertaking substantial risks. But improvements over the decades have made aviation one of the safest modes of transportation around, if only hazards from accidental crashes due to pilot error and hardware failures are considered. While every design effort has been expended to make planes intrinsically safe, modern commercial (as opposed to military) aircraft were not designed with terrorism in mind. The idea that someone inside the plane would brandish arms or set off a bomb was simply not in the imagination of design engineers until recently.

Now, of course, it is. After the World Trade Center attacks of Sept. 11, 2001, the only visible change to the structure of commercial aircraft was the presumably bullet-proof steel door that now protects the flight deck from assault from within the cabin. This was an obvious step, and cost the airlines something, but clearly isn't going to solve all of their terrorism problems. Once a person with a reasonably powerful bomb gets on board a commercial airliner, the game is over if the bomb is exploded. There is no practical way to make planes impervious to explosives detonated from within. Flying is a very weight-sensitive business, so the heavy armor required to withstand bomb-force blasts literally won't fly. And so the only way to keep planes from being blown up by terrorists with bombs on board is to keep the bombs off the planes in the first place.

But that isn't free either. Since early terrorist bombs were stowed in luggage, inspection of checked baggage by X-ray was one of the first security measures to be implemented. After the attempted shoe-bombing of an airliner, passengers got used to taking off their shoes for X-ray inspection as well. Now that the latest plot involved liquid explosives, most liquids are now banned from carryon luggage. One almost hates to speculate about these matters in a semi-public forum, but there is always the possibility of a suicide bomber who swallows a time bomb. Not even the most dedicated terrorists have gone to this extent yet, possibly because bomb technology cannot yet put a powerful enough charge into a volume small enough to swallow. But if such an infernal deed is ever done, we can reconcile ourselves to whole-body low-dosage X-rays of all passengers, which would be the ultimate invasion of privacy.

Loss of privacy, delays, inconvenience, and the high cost of inspection machinery are only some of the prices we pay for being able to fly. A company called Ahura is test-marketing a book-size device that can do a chemical analysis of any liquid that you can see, even through glass or plastic bottles. It uses a laser to stimulate vibrations in the molecules of the liquid, which in turn give off light that the device analyzes and interprets in terms of chemical composition. The process, called Raman spectroscopy, has until recently been confined to chemistry research labs. But high demand for security inspections and advances in compact computer and sensor technology have allowed companies like Ahura to develop these devices. Still, they are not cheap. According to an account in Time Magazine, the Ahura unit retails for about $30,000. It will be a while before every airport is equipped with such a device, and in the meantime, even bottled water has become a rarity in the air.

Engineers like to view a problem in enough detail to have a good idea of how design choices will affect the performance of the system in question. In the case of airline security, the system is the whole complex of air travel. The design choices include how much we will pay for increasingly sophisticated security technology on the ground, how much we charge for air travel, how much of the cost of security is borne by the government versus private sources, and (not least important) what kind of research and development we do to prepare for future security problems. This last item is currently being covered, if at all, by small private firms such as Ahura in conjunction with government-sponsored research related to terrorism. It is a well-known fact among researchers that adding the word "terrorism" to a research proposal with almost any conceivable justification increases its likelihood of funding, other things being equal. Whether or not this results in better ideas for anti-terrorism technology is so far an open question.

While the U. S. government has taken steps to coordinate anti-terrorism efforts with the creation of such entities as the Department of Homeland Security, it is not clear that such efforts are coordinated enough or directed well enough to do a good job at not only reacting to, but anticipating, new terrorist threats to airline safety. Most successful crash programs, from the Manhattan Project to the Apollo program, have been coordinated by a single, central authority with a single-minded purpose and enough resources to get the job done. Commercial airline safety differs from those programs in many ways, of course. Millions of ordinary citizens, hundreds of private companies large and small, and international relations all make it a complex picture. But whatever else it is, it is an engineering problem. And a more coordinated and focused effort to make airlines as safe from terrorists as they are now from accidental crashes would be worth whatever we paid for it. Even if I can't carry my soft drink onto the plane for a while.

Sources: The Time Magazine article "A New Way to Detect Liquid Explosives" on Ahura is at http://www.time.com/time/business/article/0,8599,1225412,00.html.