Granted, but the bulkheads between the cockpit and the cabin are still not bulletproof. The doors were simnply reinforced so that they couldn't be broken down.<quoted text>
A common misconception and old wives tale - modern planes have a redundant system designed for many small holes in a plane, which minimizes and controls the decompression and potential harmful effects. About 20 years ago a big passenger jet still managed to fly and land on Hawaii after a massive decompression at 24,000 feet due to metal fatigue ripped off a large part of its top. 95 passengers, 1 death, 94 survivors (65 injured). This is far better odds of survival than the many times when a maniac hijacker(s) has taken control of a plane.
Enter several hijackers and 150 armed passengers. Hijackers move to the front of the cabin to announce their intentions and intimidate the 150 armed passengers. Now comes the fun part- 150 armed passengers take aim and unload thier 15 round clips. Bullets fly, hijackers are ripped to shreds (Yay!), but wait- the sharpshooters from row 12 and back didn't have such good accuracy at their range and several hundred rounds went through the bulkhead and into the cockpit. Hmm, not a good day for the inhabitants of the cockpit.
Too bad the pilot and copilot don't have so many "redundant systems".