Risk Assessment
It is always going to be very difficult to design procedures to prevent deliberate sabotage of aircraft. They will never be 100% foolproof and will often have the potential to create some of the scenarios they are trying to avoid. For example;
1. Any door designed to keep out intruders will always have the potential to keep out rescuers.
2. Psychological screening will never catch every risk and if taken to extremes exclude perfectly safe pilots.
3. As most cockpit doors open inwards a determined individual will always be able to overcome a pilot swapping places with an FA and get that door locked.
We must therefore be careful to be realistic about what can be done and what the industry will be prepared to do -
1. No airline is going to add a third crew member - although that would probably be the most effective way to prevent this.
2. No aircraft manufacturer is going to add double doors as specified by EL Al - although clearly they would help significantly.
3. no regulator is going to remove the requirement for lockable doors depite the fact they have the potential in certain circumstances to create the very scenarios they are designed to prevent.
So we all know what is coming
- Low to no cost, high inconvenience reactive measures ...
1. Procedures to swap pilots with FAs as in the US cost nothing - but make life operationally complicated and will never be 100% effective. Cockpit doors usually open inwards so a determined individual could always push out an unsuspecting colleague and lock him or her out. Has the US experiment prevented any sabotage attempts?
2. Increased psychological screening. This too will never be 100% effective. It relies in part on the individual not trying to trick the assessor and if practiced in extremes would result in many perfectly safe individuals being denied their careers.
3. Fatuous justifications - for example - "we know of no incidents that have been detected but how many might have been prevented". By such justifications we could ban almost anything from flying. i.e. The 911 guys had pilots licences so should we ban pilots - a ridiculous example but it is all about a sense of proportion.
... so my point in summary
If we are not going to do something because the cost is considered too high versus the real risk, let's not do it either if it causes daily inconvenience to crew and passengers and has very little chance of preventing future incidents