Flying from Tuxtla Gutierez (sp?) to Mexico City a few years back I arrived at the airport on time to find that my flight had been cancelled, and to get a later flight would have caused me to miss my connecting flight to London. I spoke to somebody at the desk and he said:
"Eh, ningun problema senor, you can go on the next flight"
"When is the next flight?"
"Eh, about 10 or 15 minutes or something",
so he walked me straight onto the plane carrying my backpack without ever having to go through any kind of scanner or have my luggage X-rayed at all. Mexico City airport is surrounded by high-density housing so if I had had a bomb I could have taken out entire boroughs. The funny thing was that the date was 11th September (though not 2001). Love that no worries attitude.
When I was about 8 in the mid-90s I remember being allowed to go in the cabin mid-flight between England and Spain to see the cockpit and ask the pilots what the various controls were for, which was fun. I assume this would not be allowed these days.