at a huge bone yard in california's mojave desert. here's what he discovered about the doors and what the captain was up against. >> reporter: stores airplanes no longer being used here but this boeing 737 was flown after 9/11 so it has a reinforced cockpit door. we want to give you a close up look at how it works. the 737 was moth balled less than a year ago. the locking system on these reinforced doors is very similar to the locking system you would have in an airbus a 320 that crashed in france. he's the director of southern california aviation. what is this door made of? this reinforcement? >> this is an inch and a half thick of kevlar with some steel. it's a kevlar door. >> reporter: unlike the airbus this is a key lock? >> this is a key override system. >> reporter: but it has what the airbus has. a numbering system. what is that for? >> a key pad to punch in the