VIDEO: How Reinforced Cockpit Door Could Keep Out Germanwings Pilot, Despite Emergency Access Codes

(CBS SF) -- The suspected intentional crash and subsequent mass murder of 150 people at the hands of Germanwings co-pilot Andreas Lubitz is raising questions worldwide about cockpit doors and how the alleged murder-suicide by airplane may have been carried out.

After 9/11, airlines installed bullet-proof, reinforced cockpit doors with a complex set of latches, switches and even an electronic keypad, making it incredibly hard for a passenger to break into the cockpit, while still allowing for entry if both pilots became incapacitated, potentially by decompression or illness.

This video demonstrates how the doors are set up.

The doors are set up so that the pilots can lock them. A numberpad, however, allows a crew member with a code to get in.

If a pilot felt threatened, or if in this case, if the co-pilot intentionally wanted to lock out the other pilot, there is a setting on doors that overrides the number pad for a length of time, usually five to 20 minutes.

This was designed so even if a terrorist coerced a crew member to give them the code, they could still not get into the cockpit right away. Conceivably, the pilots could continue over-riding the code as long as necessary.

If the pilots lost consciousness, however, after five minutes, a flight attendant would be able to punch in the code, enter the cockpit, and attempt to revive the pilots or land the plane.

The Airbus A320 that crashed was flying from Barcelona to Duesseldorf when it began to descend from cruising altitude of 38,000 feet after losing radio contact with air traffic controllers. All 150 on board died when the plane slammed into the mountain.

Co-pilot Andreas Lubitz's "intention (was) to destroy this plane," Marseille prosecutor Brice Robin said, laying out the horrifying conclusions reached by French aviation investigators after listening to the last minutes of Tuesday's Flight 9525.

Andreas Lubitz trained in Arizona, and spent at least enough time in the Bay Area to have his picture taken by the Golden Gate Bridge.

FACE OF A MASS MURDERER: http://sanfrancisco.cbslocal.com/2015/03/26/the-face-of-a-mass-murderer-german-pilots-personal-photos-similar-to-any-other-sf-tourist/

Many wonder whether a blunt object would have been able to break through the door, but this video posted to YouTube showing what appears to be certification testing of typical cockpit doors suggests they are incredibly sturdy.

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