A fundamental safety management assumption is the need to learn from accidents, to identify their causes, and to take steps to prevent their recurrence. Safety by prevention is, however, not the only solution. Since something cannot go well and fail at the same time, another approach is to learn from situations where things go well and where “nothing” seems to happen. In the present case a computer breakdown led to the loss of most of the information in an air traffic control system. The operators managed to compensate for the missing information and keep traffic flowing, although with reduced capacity, while the technical staff managed to restart the system. The same breakdown occurred two more times during the day but in both cases the operators were able to compensate. In the evening the computer system was restored and no further breakdowns happened. The organisation investigated the event but since it focused on the technical issues the lessons learned were in terms of new checklists, improved procedures, and stricter precautions. The paper presents an analysis from a different perspective that looks at what went well. This identifies a number of things that may contribute to make performance in the future even safer.

一个基本的安全管理假设是需要从事故中吸取教训，确定其原因，并采取措施防止其再次发生。然而，预防安全并不是唯一的解决办法。由于某些事情不可能同时进展顺利和失败，另一种方法是从事情进展顺利和似乎“什么都没有”发生的情况中学习。在本案中，计算机故障导致空中交通管制系统中的大部分信息丢失。操作员设法弥补丢失的信息并保持流量畅通，尽管容量有所降低，而技术人员设法重新启动系统。同样的故障在白天又发生了两次，但在这两种情况下，运营商都能够进行补偿。到了晚上，计算机系统恢复了，没有发生进一步的故障。该组织对事件进行了调查，但由于它专注于技术问题，因此吸取的教训是新的检查清单、改进的程序和更严格的预防措施。这篇论文从不同的角度进行了分析，分析了哪些方面进展顺利。这确定了许多可能有助于提高未来性能的因素。