Hold on a second...
Even though many current critisizms of overzealous, incompetent, and power-tripping screeners are legitimate, it's COMPLETELY unfair to hang the events of 9-11 on them, even in part. The implements used by the homicide hijackers (box cutters with < 4" blade) were LEGAL to carry aboard at the time.
But even if they had been illegal (like they are now) and confiscated at the security checkpoint, the hijackers still would have posessed the two critical weapons they used that day. The first was THE WILL to carry out their plan, killing individuals (flight crew)at close-quarters in order to commit suicide/homicide on a massive scale. In fact, this could even be accomplished with nothing more than bare hands and/or pens by a team of commited individuals.
But that willingness alone would not have worked had it not been for the REAL key to their success, which was OUR OWN policy of "passive-resistance". The hijackers KNEW this policy, developed as a response to the "Take me to Havana" scenario of the 1970s, would play into their hands because ultimately, it DICTATED COMPLIANCE WITH THEIR DEMANDS, so therefore afforded them the window of opportunity they needed. That policy DID NOT FACTOR IN commited, planned suicide.
Even the attempted-murder/suicide by using a FedEx DC-10 as a weapon a few years ago, and 20 yrs of suicide-bombings did nothingto change the arrogant attitude of the supposed, self-proclaimed "experts" who set policy and mandated compliance to it. Their self-blinding "insight" into the realm of terrorism and what makes those people tick ASSUMED that hijackers were too stupid to learn how to fly an airplane, even at the most rudimentary level needed for the PURPOSE of crashing it. The security "experts" in government and airline training departments (usually ex-fed law enforcement agents safe on the ground) REFUSED to address this possiblity because it didn't fit into their neat, little box of scenarios.
Pointing out that responding to that mandated, ultimately-compliant policy in response to those commited to real-world, planned murder (such as with FedEx) was tantamount to a "lambs-to-the-slaughter" approach, threw a big wrench into the theororetical world they live in where their policies always met with success. They didn't want to hear any argument, and those expressing doubts were met with condesceding answers.
It took 9-11 to change that idiotic, smug policy throughout the industry, and therefore took away any would-be terrorist's greatest weapon. We now consider the cockpit to be a castle keep that WILL be defended under any circumstance and with all available means. Pax realize this and they too are willing to stand in defense. This is OUR most effective tool against another 9-11-style attack....the deterrence created by the terrorist's awareness that their chances of real-world success have been dramatically reduced because of OUR WILL (pax included), and the days of lambs-to-the-slaughter are GONE. In fact, those days ended on 9-11 also, aboard the United flight that crashed in PA.