However, if you ask me, this is one of the more positive things TSA has done in a long time, and will make the checkpoint process at least marginally less tedious. That some are opposed to the changes is not surprising, but the backlash strikes me as counterproductive.

The decision has raised the ire of some, including flight attendant unions, who have called the decision reckless and dangerous.

Last week, the Transportation Security Administration (TSA) announced it would rescind its longstanding ban on the carriage of small knives. Effective in mid-April, passengers can once again carry implements with blades of up to 2.36 inches onto airplanes.

TSA is all mealy-mouthed when it tries to explain why, exactly, it has decided to relax the ban. They might not be willing to admit it, but they seem to have come to terms with two simple truths.

The first is that a potentially deadly sharp object -- a knife, if you will -- can be improvised from virtually anything, including no shortage of materials found on airplanes. Even a child knows this.

I don't want to seem cavalier. I work in this business and the safety of my colleagues and passengers is paramount. But let's be realistic: there are thousands of ways to contrive a dangerous weapon. There has never been any point, pardon the pun, in rummaging through people's bags to confiscate small hobby knives and scissors when an equally lethal implement can be made from a broken first class dinner plate, a wine glass, a snapped off shard of plastic, and so on. The ban was a knee-jerk reaction to the 2001 terror attacks, and it made little sense from the beginning. Easing the rules will free up time and resources, allowing TSA staff to concentrate on more legitimate threats.

The second truth is that, from a terrorist's standpoint, the September 11th blueprint is no longer a useful strategy.

One of the grandest and rarely acknowledged ironies is that the success of the September 11th attacks had almost nothing to do with airport security in the first place. Conventional wisdom holds that the attacks succeeded because 19 hijackers took advantage of a weakness in airport security by smuggling boxcutters onto jetliners. And conventional wisdom is wrong.

What the men actually took advantage of was a weakness in our thinking, and our presumptions of what a hijacking was, and how one would be expected to unfold, based on the decades-long track record of hijackings. In years prior, as many of us remember, a hijacking meant a diversion, perhaps to Havana or Beirut, with hostage negotiations and standoffs; crews were accordingly trained in the concept of âpassive resistance.â

The presence of boxcutters was merely incidental. The men could have used anything, from broken plates to sharpened ballpoint pens -- particularly when coupled with the bluff of having a bomb. Their plan relied almost entirely on the element of surprise, not weapons. And so long as they didn't chicken out, their plot was all but guaranteed to succeed.

They didn't chicken out, of course, and it worked. But such a scheme is no longer viable. Those opposed to the changes keep reminding us about September 11th, and how flight attendants were the first people murdered on 9/11, with small blades. Indeed, but it does not change the fact that, as a tool for a suicide hijacking, knives today would be useless. The hijack paradigm was changed forever even before the morning of September 11th had ended, when the passengers of United flight 93 realized what was happening, and fought back. Because of the awareness of passengers and crew, together with armed pilots and barricaded cockpits, the idea that a jetliner could again be commandeered using knives is too ridiculous to entertain. This was not the case in 2001, but it certainly is true today. We have to remove this discussion from the framework, and the emotional weight, of September 11th. It is no longer about that.

If you want to talk about the danger of knives as a tool for ordinary assault, such an during an âair rageâ incident, thatâs more reasonable.

But again, a 2.3-inch blade is no more dangerous than any of countless weapons a person could use. Air rage can sometimes escalate to violence, but how many crew members are stabbed by angry passengers each year using, for example, any of the tens of thousands of metal knives and forks that are handed out each day with inflight meals? Nobody is suggesting we should facilitate violence on planes, but the idea that permitting the carriage of small knives and tools is going to cause the number of random inflight stabbings to suddenly spike is groundless and unrealistic. Meanwhile, there's not only a common sense aspect to this, but a common good aspect as well: the common good of streamlining and rationalizing security.

I have no idea if TSA's thinking took any of this into account, but I imagine so, even if they're reluctant to admit it. It's a smart and refreshing way of approaching things, which is something we're not used to when it comes to airport security.

Iâm not writing from the perspective of a pilot, safely ensconced in a protected cockpit. Iâm writing from the perspective of reason, and in the collective interest of everybody who flies. I appreciate the hard work that flight attendants do, and I realize that passengers are sometimes disruptive or aggressive. But we need to get past the emotionally charged style of security-think that ultimately makes us less safe. These new measures are sensible, and meanwhile TSA can, or should, concentrate or more potent threats to safety â your safety as well as mine â such as bombs and explosives.

If there's one potential downside, it's the complexity of the revised rules. There are stipulations for blade length, blade width, handle type, whether a knife has a locking mechanism, etc., most of which are unnecessary in light of the points made above. I'd like to think the changes will speed up the checkpoint lines, but that depends how obsessive TSA guards are going to be when it comes to specs.

This is ironic, isn't it? Poor TSA is damned if it does and damned if it doesn't. We rant about the agency's refusal to enact rational measures. Here they're doing it, and people are angry.



By the way, if you're wondering where 2.36 inches comes from, that's 6 centimeters. TSA's liquids and gels restrictions are also based on metric measurement.

Earlier this year, on the Silver Line buses between Logan Airport and South Station, a recorded announcement was played reminding passengers about the restrictions on liquids and gels. Riders were warned that liquids, gels, and aerosols must be in containers of "three point zero ounces or less."

Not quite. The max container size is not 3 ounces, as is commonly believed. It's 3.4 ounces, or 100 ml.

Those travel-friendly containers you buy at CVS are cheating you out of nearly a half ounce!



For more, see my essay: TERRORISM, TWEEZERS, AND TERMINAL MADNESS