Formalism helps in describing accidents

We analyse the 'probable cause' of the 1979 Chicago DC-10 accident using a minimal formalism, and find an omission. The omission is contained in the body of the report. This omission had consequences for the public discussion of this accident, which we show. We conclude that formalism helps in accident reporting by enabling simple consistency and omission checks. We then present a quick overview of our formal method, Why-Because Analysis, which provides the necessary mechanisms and rigor. We consider this to be the engineering of causal reasoning. As is now known from a quarter-century's experience with verification of digital systems, such reasoning engineering is both essential and non-trivial.