honestly, if i was a terorist who happened to invest many years of my life building 1000's of hrs in aircraft to eventually get the right hand seat of a commercial airliner then WHY WOULD YOU BOTHER TAKING THE RISK OF SNEAKING EXPLOSIVES ON BOARD?
you are one of only 2 people in command of an aeroplane. you could incapacitate the other (if he/she wasnt a terrorist too), turn off A/P and drive the thing right into the ground....