This talk presents the findings of two case studies on the topic of crisis communication on Twitter. It is based on two customised corpora of tweets that customers directed at British companies as well as their social media managers’ replies. The first case study takes a closer look at Southern Rail, a British company operating trains in the South of England that was repeatedly subject to industrial action in 2016 and 2017. The second case study focuses on the interactions evolving on Twitter due to an IT systems outage that the airline British Airways experienced in May 2017 and that led to cancellations and delays of its normal service provision for several days. The aim of this talk is to show how customers addressed these incidents, which threatened the companies’ reputation as reliable train and air travel providers, and how the companies responded in order to maintain their legitimacy in the face of crisis.