[reirob]

Interestingly and off topic, the same lock that is intended to prevent take over of a plane, was used by a pilot to crash the plane and kill all 150 people [1]:

> The crash was caused deliberately by the co-pilot, Andreas Lubitz, who had previously been treated for suicidal tendencies and declared "unfit to work" by his doctor. Lubitz kept this information from his employer and instead reported for duty. Shortly after reaching cruise altitude and while the captain was out of the cockpit, he locked the cockpit door and initiated a controlled descent that continued until the aircraft impacted a mountainside.

[1]: https://en.m.wikipedia.org/wiki/Germanwings_Flight_9525

[stjohnswarts]

Nothing is 100%. Clearly the chances of leaving doors wide open is much more dangerous than locking them.