Robert Lemos

It’s Friday morning and things have become a bit clearer. Law enforcement officers in the U.K. have arrested 24 people suspected of planning to blow up planes using liquid explosives disguised as drinks, hair gel and other consumer products.

The new restrictions can be found on the U.S. Department of Homeland Security’s site. As an aside, I’m working from California this week, so I’m going to experience the new security restrictions first hand when I return.

Carry-on luggage is different from check-in luggage in two ways (Eric Rescorla has a good post on this):

1. Access: People can access the contents of their carry-on luggage at most times during the flight.
2. Different security process: Carry-on bags are generally processed in a different, and less intensive, way than other bags.

The first question that comes to mind is whether the new security measures will actually help anything. In the short term, the restrictions make sense. In the long term, such restrictions could have some impact. A more general restriction on, not just liquid and gels, but any solid of a certain size that seems amorphous on the x-ray machine might limit explosives to quantities that have no chance of endangering planes.

Is it possible to actually vet passengers for all explosive materials? Likely not. A pea-sized piece of high-yield explosives could probably blow out a window at the very least. Could a dedicated terrorist hide that somewhere on his or her body–or inside, for that matter–so as to escape detection? Definitely.

And other weapons exist. Counterterrorism experts that I have interviewed have already mentioned pieces of specialized plastic that look identical to credit cards but have a sharpened edge that could act a knife. Such a blade would be more deadly than the actual boxcutters used in the original hijacking that led up to the 9-11 attacks. At the Black Hat Security briefings in Las Vegas last week, another expert described a homemade rail gun–which fires projectiles using magnetic fields–that could be made out of a pen, wire, a few capacitors and a battery. Could such a weapon make it through security? Likely. Could it take out a window? Maybe.

As most people in the security industry know, there is no way to eliminate risk. But as most businessmen know, a good business has to balance risk versus the economic impact of mitigating the risk. As these security measures build up, we are reducing smaller amounts of risk at greater and greater cost.

While al Qaeda terrorists seem to aim for coordinated attacks that have graphic impact (read: many deaths), the real impact of their latest plan is economic. More intensive carry-on security checks will likely make traveling less convenient, dissuading many customers from flying. The checks also represent a “dead-weight cost”–as one economist categorized many security measures in a recent article of mine–to the economy, mitigating a risk that might never arise.

I’m sure these are issue that airlines are quickly bringing up to the Bush Administration, so I’m sure–once the knee-jerk responses have passed–that a workable plan will be developed.