I would imagine some sort of fault tree analysis. Safety engineering in complex systems does that a lot: you start with an event you don't want to happen, imag

I would imagine some sort of fault tree analysis. Safety engineering in complex systems does that a lot: you start with an event you don't want to happen, imagine all the ways it could happen, estimate the probabilities of each contributing factor, and do the math. http://en.wikipedia.org/wiki/Fault_tree_analysis http://en.wikipedia.org/wiki/Fault_tree_analysis It sounds like one of their incoming assumptions--a probability, a manufacturing spec, something like that--didn't match up with reality. That happens. They're probably going over the fault tree, madly trying to figure out which one and by how much.