At the risk of taking this into a political area... and if I do, mods feel free to delete this post.... I spent 14 years with a major passenger airlines as a ramp supervisor, cargo supervisor and cargo agent. It's my firm belief that our next big threat isn't going to be through the passenger terminals. TSA is doing as good a job as they can, given the tools they have, the attitudes of the people, etc.... but if terrorists really want to bring a plane down, they will figure a way to get their explosives and such on board the aircraft from the ground side.
I worked for my carrier in the pre-TSA era when it was still possible to smuggle a gun on board, we had sky marshals on most flights, and even some armed couriers. I worked a flight inbound to SF via LAX where the hi-jacked demanded to be taken to Korea... he had a gun and was threatening the crew and passengers. I don't know if he actually got into the cockpit... but in those days they were not as secure as today... The captain was very calm and matter of fact with him... he told him that
1.. that particular aircraft did not have Doppler radar capable to fly over water, and that he as a captain wasn't not a qualified international pilot.
2.. the aircraft did not have enough fuel to cross the pacific..
3.. he could land the aircraft in SF and make arrangements with the station to provide an international qualified aircraft and crew.
I was working FIC (flight information coordinator) that night and got the call from the captain that he was being hijacked.... we had a 6" thick notebook of procedures... I woke up the president of the company, chairman of the board, about 6 vice presidents, the FBI, and I don't know who else.... I was on two phones, the radio and slapping FBI hands to keep them off my phones while I worked the procedures.
In the end, there was a Brinks guard courier on board who had a 38 in his briefcase... just as the aircraft touched the ground, he jumped up and shot the hi-jacker... All this started at about 2:30 am and by the time I got done with all the phone messages, paperwork, delay messages, report messages, getting the morning started for the day flights, etc.... I finally got off about noon or 1 pm.... one long night.