It is quite simple really nowadays.
Anybody suspected of being upto no good is going to be lynched by the other passengers. Pretty damned quick.
It has happened several times in the last few years.
When was the last incident in Western Europe that involved a Hijacking or REAL terrorist incident?
I cannot remember, was it Richard Reid in Dec 01?
I would not want an armed sky marshall on my flight. How do you know that they havent lost the plot through marriage difficulties etc?
I am sure that a great deal of people on here have never seen the effect of a "short" on flesh etc. Due to the slower velocity the range is a lot shorter. A wet balnket will stop a browning 9mm at about 40m, however the slug at short range could in theory punch out a window. Then the problem becomes far worse. Old Airframe, High cycles, Aloha Airlines style decompression.
I would not work for a compay that insisted on armed guards aboard.