First, the events of Tuesday were not typical hijacking's. They were suicides. Secondly, the best deterent to hijackings in general (which we have very, very few of) would be to have SECURITY PERSONEL on each flight in combination with tight physical security at the airports.
In this case, one person with a gun or a tazer on each of these flights would have prevented any of these planes from being taken over. However, the federal government in it's infinite wisdom could not find the money out of a 2 trillion dollar budget to provide security to more than a handful of flights, nor could it see the clues that pointed to this type on incident taking place.
Let's face it, the federal government is incompetent in just about everything that it does and is indirectly responsible for these events.
---max
They're pretty good at taking our money and wasting our money.