Most of the IT-Plans focus on mitigating the outage itself (e.g. multiple uplinks, backup server, fallback datacenter). I argue that critical system shall gra

Most of the IT-Plans focus on mitigating the outage itself (e.g. multiple uplinks, backup server, fallback datacenter). I argue that critical system shall gracefully handling the outage. If a client caches the flight/passenger data (lets say two weeks) you can print list. Grab a pen and keep going. That is enough for some hours and even days. If you're going advanced you can allow to add (right at the gate/counter) one person to more passengers and so on. You can also go all-in and add code which allows merging of external data i.e. allowing headquarters and airport personnel working at same time. Die Fluggäste wurden auch nicht per Strichliste in die bereitstehenden Maschinen gelassen, weil nach Angaben des Personals wichtige Informationen zum Abflug fehlten. If it works that is an appropriate solution. PS: We cannot see circumstances. Maybe a hack, a burning datacenter, war, co-worker going crazy, international sanctions, storm, flooding, whatever. For example Deutsche Bahn itself suffered recently a sabotage, two entirely independent glass fibers get cut off at same time (one in west-germany, one in east-germany).