... the meta detectors are desensitised below the knees because of the amount of metal in footware like walking boots
Granted there are many flaws in airport security, but that isn't one of them. The magnetometers will pick up metal in shoes.
... you cant really win...
This is the attitude of helpless passivity that infiltrates a society that has given up too many freedoms and too much self-reliance. Even for those of us who personally aren't so inclined, it's been imposed on us with legal restrictions.
Since it was more likely that the knife was at the throat of a stewardess, I doubt that he would have started a firefight in the cockpit since most people operate on the where there is life there is hope assumption. An airline pilot is unlikly to ensure the certain death of a colleague or passenger until the hijackers demands are established. That is how he would have been trained...
The five hijackers pepper-sprayed and slashed two flight attendants and killed an Israeli passenger. The first officer heard screaming and went back into the cabin. They cut his throat and laid him in the aisle. The hijackers went into the cockpit and cut the captain's throat. They left his body in his seat while one of them flew the aircraft from the first officer's seat.
Defense of a cockpit is not just common sense, it's a relatively simple defensive problem. The attackers must gain entry by either force or subterfuge, and come through a small opening one at a time. The the folks on 9/11 were caught off guard, but it would be beyond foolish to let it happen again. If John or any of the other pilots had known what we know now, they could have maintained control of their airplanes. Some countries have trained and equipped at least some of their pilots to prevent a repeat performance. Britain has not. It blows my mind.
It'll be a couple days before I can respond again, I'm off to fly a 767. Hijackers may take my airplane, but I hope there will be some nasty carpet stains before they do.