[bvw]

You can't secure the cockpit completely -- the crew can be tricked or blackmailed into coming out of the cockpit.

[supercat]

You can't secure the cockpit completely -- the crew can be tricked or blackmailed into coming out of the cockpit.

The toughest part of an armed pilots' training would probably be drilling in the fact that their first and foremost goal is to keep control of their 100-ton missle, even if knife-wielding terrorists are slaughtering passengers in the cabin (i.e. no matter what the terrorists are doing in the cabin, don't leave the cockpit!)