One of the long-standing debates in disaster science and practice is the tension between planning and structure on the one hand and flexibility and adaptation on the other in maximizing the effectiveness of response operations. This research aims to reconcile the divide that currently exists among scholars and practitioners and present a continuum that bridges the above models and ties planning, improvisation, and spontaneous planning together. The main questions that were examined with this research are: First, what role did spontaneous planning and improvisation play in responding to the two disasters. Second, in what ways do hazard characteristics (e.g. speed of onset and scope of impact) influence the roles played by spontaneous planning and improvisation? This is a qualitative study that employed a comparative case study to examine the characteristics of spontaneous planning. The major findings are that spontaneous planning does occur and that variables such as speed of onset, scope, magnitude, and number of organizations involved impact the visibility of spontaneous planning characteristics.