The role of data in influencing the safe operation of systems is just as important but has not attracted the same level of attention; there is no standardisation and little guidance on how the risks associated with data should be managed. There has been a marginalisation of data (inadvertent or otherwise) as a contributor to accidents and incidents, and it is clear there is an “elephant in the room” (Hampton and Parsons 2015). The problem is becoming more acute as many types of data are now used to specify, deploy, configure, operate, test and justify safety systems, moreover the volume of data in systems is also growing at an unprecedented rate. This paper is a retrospective reappraisal of selected historical accidents from the aviation and marine sectors, but viewed afresh from a data perspective. The paper shows that we do have a data problem; in fact we’ve always had a data problem.