Disasters are often precipitated by insufficient preventive care. We argue that there is a problem of prevention in that this lack of care often stems from agents’ rational calculations. Positive experiences lead agents to underestimate the risks of disasters; technological improvements and redundancies designed for safety induce agents to reduce their care. Although lower care increases the chances of an accident, the number of redundancies can be adjusted to offset this. However, the accident probability remains constant even as ostensible improvements in safety are made. Checklists can be used to decrease the number of accidents.