[stackj]

Ernie,

The Coast Guard (and it's Auxiliary) uses a model called Swiss Cheese to say the same thing. The example uses slices of cheese to represent occurances during a flight. If the holes in the successive slices line up, there is a corridor to an accident or incident. Any one slice being repositioned can block the corridor thereby preventing the accident.

The key is to recognize a building situation and take action to prevent it's progress.