Every time I fly these days, I think of Richard Reid. Also known as Abdul Rahim, he's the English-born convert to a distorted form of Islam who boarded a flight from Paris to Miami just before Christmas two years ago.
When he had settled into seat 29J, Reid-Rahim started lighting matches to ignite the plastic explosives packed in his shoes. Fortunately, a flight attendant saw what he was up to and acted accordingly. There were 20 children among the 197 people whose lives were saved.
The good news is that Reid got a life sentence in Boston last month. I can be as liberal as the next person, but I felt like cheering District Judge William Young to the rafters. I would not be Uncle Sam's Number One fan either, but when the judge, pointing to the Stars and Stripes, told the defendant that it would still be there long after his miserable deeds were forgotten, I found myself saying with approval: "You tell him, boy."
The bad news is that, thanks to Reid-Rahim, air travel has become even more like trying to negotiate your way through a border post in the middle of the second World War. On a recent transatlantic journey I was told to take off my shoes for examination prior to boarding both the outward and return flights. This is something I associate with old movies about steamy police cells in the American Deep South, where racist cops degrade their unfortunate captives by obliging them to remove their footwear.
No doubt it is necessary for airport security, and we must therefore accept it, but it is still humiliating. It is not so long ago that air travel was presented as a rather grand experience and glamorised in Art Deco posters as a type of superior cruise, the QE2 with wings.
But that's not all, as air passengers know only too well. Heaven help you if you have a laptop computer. At most airports, you will be asked to turn it on. Hopefully, your battery is not dead, or you are in trouble. When the security official sees that the computer works normally and does not contain explosives, he or she turns to the next passenger. All very well, except that it's easier and quicker to turn a computer on than off. There you are, fumbling with the controls, waiting for the darned thing to switch itself off, and conscious of the line of people coming after you.
It is all in a good cause, of course, and these are petty complaints when compared to the scale of any possible disaster. Air travellers must submit cheerfully to the ever-growing list of indignities, although getting on a plane is becoming more and more like one of those SAS obstacle courses on television.
I do not envy airport security workers their daily burden of repetitious boredom and heavy responsibility. The slightest deviation of attention, the least departure from the highest standards of scrutiny, could lead to disaster.
But while there have been some reports of lucky finds lately, such as the hand-grenade allegedly found in the luggage of a passenger flying from Venezuela to London, I wonder if we are not fooling ourselves in the long run.
Since the 9/11 hijackers showed the lethal use that could be made of Stanley knives in mid-air, we are all being asked if we have sharp objects in our luggage. I notice that, at mealtime on the plane, the knife is always plastic, even when the fork is metal.
But what if our would-be hijackers are skilled in martial arts? We all know that the 9/11 group was big on training. It would not be difficult for terrorists to learn how to disable or even kill crew-members or fellow-passengers with their bare hands. Another option would be to strangle someone using a simple necktie or garrotte. Alternatively, we have been warned that someone may be taking aim from the ground with a heat-seeking missile.
There is, in short, no such thing as total aircraft security. The example of Richard Reid shows that the terrorists are always one step ahead and that the price of safety is endless, nerve-wracking vigilance.
Prevention is better than cure, and there is another factor, less easy to define, which also plays an important part in creating security, both in the air and on the ground.
We live in an international political climate where young people of extreme fundamentalist views are taking desperate action by land, air and sea to advance their political and religious aims. They do it largely because they hate the USA and, by extension, Israel, which they regard as an American province. I have come across some of these youngsters in my travels, gentle, softspoken folk quite often, until they speak of the "Great Satan" of US imperialism which has become, like England for Wolfe Tone, "the never-failing source of all our political evils".
The trouble is that the US brings many of these troubles on itself - by its failure to tackle the Israeli-Palestinian conflict, its history of interference in other countries, and the widespread feeling that all Washington cares about is oil and power. Iraq is only the latest example. The skies will be no safer after the downfall of Saddam Hussein, probably less so. So, next time you fly, remember to pray and wear slip-on shoes.