That would be hard to pull off. The cockpit door is rarely open during flight, and when the cockpit door needs to open, the flight attendants barricade the fron

That would be hard to pull off. The cockpit door is rarely open during flight, and when the cockpit door needs to open, the flight attendants barricade the front of the plane using the food service carts locked diagonally across the isle. The door itself is only open for a few seconds, and the barrier is enough to shut it quickly if anyone even attempts to move towards the front.