The current airline restrictions are a joke. The last hijackings took place with utility knives. Do you know how EASY it is to get a utility knife onboard? How small a blade is for one of those?
Give me half an hour, and I’ll make a utility knife that I’d be willing to bet $1000 of my own money that I could get through security, even if they knew I was a high risk to be carrying a weapon. The removable blade gets slid into my laptop between the metal RF shield and the plastic case. It won’t show up on an X-ray. The handle for the knife is made out of a couple of snap-together plastic parts. I’ll slide them inside a 3.5" floppy disk, and put the disk in the laptop.
Using this technique, I could get 5 or 10 utility knives on board in a single laptop, and distribute them to my compatriots on board.
Need some more weapons? No problem. First, take the battery pack out of your laptop, and install some smaller batteries wired in parallel so that the laptop still works when switched on (for about 10 minutes). The rest of the hollow space is lined with steel to prevent an X-ray shadow of what’s inside (laptop batteries are opaque to X-ray, which is why they are making people turn them on - the contents of the battery is not knowable). The hollow space inside the battery pack would be small enough for a .25 caliber automatic pistol.
Need some more weapons from your laptop? No problem. A couple of windings of wire around the inside of the case, with loops on the end for some toggles, and I have a garotte that will kill you faster than the utility knife will.
More weapons? No problem. Tell me what you need, and I’ll figure out a way to get it on board. Hypothetically, of course. Don’t try this at home, kids.
You can never ensure your security this way, if you define security as the requirement to get rid of the type of weapons the terrorists used, and other weapons of similar lethality. It is literally impossible. Hell, the arm of my eyeglasses would make a fine dagger. Just remove the plastic ear guard, file the metal to a sharp point, and put the guard back on. When you get aboard, you bend the glasses in half between the lenses so that the arm sticks out past the end. Wrap a piece of wire around it to hold it in place, and you have an instant weapon.
Hell, you don’t even need a metal knife. Take a laptop, and just scribe a line on the inside of case in the shape of a sharp pointy thing. Get on the plane, and flex the case - the plastic will break on the scribed lines, and you have an instant weapon - a nice hard plastic blade that will easily penetrate a human.
This whole enhanced security thing is a HUGE waste of resources. The best security change for the airlines we got for free, when the passengers of flight 93 brought that plane down. The terrorists know that they’ll never get away with another hijacking like that, because the passengers will fight them to the death. So it ain’t going to happen. We’re just wasting our money, and focusing all of our attention on the LAST weapon. That’ll give us a false sense of security so that we’ll be even more unprepared for the next attack.