IN AMERICA AND ACROSS MUCH OF THE WORLD, the security enhancements put in place following the catastrophe of September 11, 2001, have been drastic and of two kinds: those practical and effective, and those irrational and pointless.

The first variety have taken place almost entirely behind the scenes. Comprehensive explosives scanning for checked luggage, for instance, was long overdue and is a welcome addition. It's the second variety, unfortunately that has come to dominate the air travel experience. I'm talking about the frisking, X-raying, body scanning, and confiscating that goes on at thousands of concourse checkpoints across the globe — activities that by and large waste our time, waste our money, and humiliate millions of us on a daily basis.

There are two fundamental flaws in our approach:

The first is a strategy that looks upon every single person who flies — old and young, fit and infirm, domestic and foreign, pilot and passenger — as a potential terrorist. That is to say, we're searching for weapons rather than people who might actually use weapons. This is an impossible, unsustainable task in a system of such tremendous volume. As many as two million people fly each and every day in the United States alone. Tough-as-nails prison guards cannot keep knives out of maximum security cell blocks, never mind the idea of guards trying to root out every conceivable weapon at an overcrowded terminal.

The second flaw is our lingering preoccupation with the tactics used by the terrorists on September 11—the huge and tragic irony being that the success of the 2001 attacks had almost nothing to do with airport security in the first place. As conventional wisdom has it, the 9/11 terrorists exploited a weakness in airport security by smuggling aboard box cutters. But conventional wisdom is wrong. It was not a failure of airport security that allowed those men to hatch their takeover scheme. It was, instead, a failure of national security — a breakdown of communication and oversight at the FBI and CIA levels. What the men actually exploited was a weakness in our mindset — a set of presumptions based on the decades-long track record of hijackings and how they were expected to unfold. In years past, a hijacking meant a diversion to Beirut or Havana, with hostage negotiations and standoffs; crews were trained in the concept of "passive resistance." The presence of box cutters was merely incidental, particularly when coupled with the bluff of having a bomb. They could have used knives fashioned from plastic, broken bottles wrapped with tape, or any of a thousand other improvised tools. The only weapon that mattered was the intangible one: the element of surprise. And so long as they didn't chicken out, they were all but guaranteed to succeed.