In a world characterized by complex interdependence, crises that originate in one country have the potential to rapidly diffuse across borders and have profound regional and even global impacts. The eruption of the Icelandic volcano Eyjafjallajökull in April 2010 demonstrates how rapidly a natural disaster can morph from a local crisis with local effects to a cascading crisis with international effects across multiple sectors. After spreading to Europe the ash cloud severely disrupted air travel and paralyzed the European aviation transport system. This cascading crisis caught authorities by surprise and revealed the need to improve crisis preparedness to deal with the threat of volcanic ash in particular and aviation in general at the international, EU, and national levels. In the aftermath of the event, reforms and policy changes ensued. Just over a year later, the Icelandic volcano Grímsvötn erupted, providing an opportunity to observe the revised system respond to a similar event. The origins, response, reforms, lessons learned, and questions of resilience connected to these complex negative events are the subject of this paper. The article concludes by addressing the question of whether and to what extent the vulnerabilities and problems exposed by the 2010 volcanic ash cloud event are amenable to reform.