There are three BIG things that the government refused to allow that would have prevented 9/11/2001:
Armed pilots
Profiling
Fire incompetent federal workers
The US Government KNEW there was heightened activity by Al-Qaeda within the United States. Al-Qaeda members consist mostly of MIDDLE EASTERNERS! But nooooo -- we surely couldn't profile, that would be 'racist', even if it does save lives.
Many, if not most, airline pilots are former military and all military go through basic training and learn how to handle firearms. In addition, these planes were hijacked by 4-5 individuals with BOX CUTTERS! The very things that allow us to break down cardboard boxes got the 4 planes hijacked. An armed pilot, co-pilot and navigator more than likely would have been able to stop this with bullet diplomacy. To this day, pilots still aren't armed. For what it is worth, pilots USED to be armed before the Lyndon Johnson Era.
Fire incompetent federal workers. Somewhere along the line communication broke down and the word from that one FBI official regarding Middle Easterners taking flying lessons but not learning how to take off or land did not get enough in the organization to set off flags. This points to incompetence and negligence by the federal government. More than likely, those negligent employees are still in their 9/10/2001 jobs or even promoted! Firing government workers is harder than firing tenured teachers! Government should NOT be a jobs program, it should be just like the private sector, if you aren't excelling, then you're job searching. Too many in government are the lowest common denominator of society. When it comes to protecting this nation, this is unacceptable. Disclaimer: I don't consider the military to be government workers, these are defenders of freedom..
Armed pilots
Wouldn't have helped in the slightest. "Armed pilots" is a simplistic mantra for the knee-jerkers and bunker kooks out there, nothing more. The terrorists could have used any number of methods to overcome an armed pilot; rushing the cockpit en masse, laying down smoke, a stun grenade, or CS and obscuring the pilot's view, or simply blowing up the plane from where they sat or threatening to do so unless the pilot came out of the cockpit unarmed.
There are inadvertent discharges of firearms every day in the military, on police forces, at private ranges, and in private homes and businesses. How many airliners full of passengers downed by a stray round are worth the dubious "safety factor" of thrusting a .38 Special into the hands of every pilot whether he wants it or not?
When I was taught how to handle a firearm, one thing that was drummed into MY head was "Simply having a firearm does not make you Rambo or invincible."
Profiling
Ah yes, I was wondering when you were going to get around to this one. In America, people are innocent until proven guilty. Sorry to hear about the country you apparently hail from.
Fire incompetent federal workers
Even Superman wouldn't have been able to foresee and prevent at least four separate hijackings, all on the same day, all unexpectedly, all employing a devastating new type of attack on American property and people. 9/11 was the bellwether of a new type of war. And, sitting back and attacking the people fighting that war like you're doing isn't helping us win the war.
If you (and the LP) have all the answers to terrorism as you claim, then you should either go to work for the federal government and start enacting your wonderful ideas, or start garnering more than .03 percent of the vote in national elections and do it via the ballot box. Until you do, you in particular and libertarians in general remain the crazy uncle in the attic of American politics.