It's certainly not the first time in the last year that the safety of air travel has been brought into question. But as it's revealed the Germanwings plane was brought down on purpose by the co-pilot, Katie Gregory asks if anything could have been done to prevent this latest tragedy.
It's a system supposed to protect passengers and pilots. The cockpit door in an Airbus A320 can't be opened from the outside without a code. But that code can be disabled from inside the cockpit. This is the situation the captain of the doomed Germanwings flights faced - as he was shut out of the cockpit by his co-pilot - according to German Transport Minister Alexander Dobrindt. (SOUNDBITE) (German) GERMAN TRANSPORT MINISTER, ALEXANDER DOBRINDT, SAYING: "The doors are technically set up so that they can always be opened from the inside. When that is not possible there is the option of opening the doors from the outside with a code unless this is explicitly blocked from the inside. As you know, these exact rules were introduced after 9/11 and the technology was fitted into planes." After locking out the Captain, the co-pilot's believed to have purposely crashed the plane. According to aviation security expert Professor Norman Shanks ... this incident will call into question not only the door locking regulations - but also staff hiring procedures. (SOUNDBITE) (English) COVENTRY UNIVERSITY, AVIATION SECURITY EXPERT, PROFESSOR NORMAN SHANKS, SAYING; "I suspect this will be a key turning point, that airlines will now have to think about measures to ensure that there is never an occasion when only one person is in the cockpit. So it's relatively easy to do for short haul flights. In longer flights it may mean re-instating the third pilot or someone else who is pilot trained that can stand in when one of the pilots has to leave." But a third pilot comes at a cost. (SOUNDBITE) (English) COVENTRY UNIVERSITY, AVIATION SECURITY EXPERT, PROFESSOR NORMAN SHANKS, SAYING; "Germanwings has a policy that when one pilot needs to leave it should only be for as short a time as possible. Other's have a policy of absolutely no one leaving, so both pilots remain in the cockpit. That's something that needs to be addressed and it can be addressed now, overnight." Germanwing's parent company - Lufthansa - says all its pilots undergo annual medical checks, but not a "specific" psychiatric assessment. The big question is - whether airlines could ever accurately determine and predict staff behaviour? NATSOT of SEARCH The Germanwings crash is now a criminal investigation. And airlines are already reacting - budget carrier easyJet has just introduced new rules to ensure two crew members are in the cockpit at all times.