This document guides you in the implementation of a Just Culture. It also helps you identify some possibilities for creating national and international Just Cultures. This is important in aviation, because experience has shown that we can learn immensely from honest mistakes. But that means they need to be reported—freely, without fear of retribution. Indeed, ideas about Just Culture, most prominently, feature openness and information sharing. All definitions of a Just Culture draw a line between acceptable and unacceptable behaviour. This line, however, is also exactly what makes a Just Culture hard to implement. That which determines a Just Culture can also undermine it.