As the impact and complexity of disasters, either natural or man-made, have increased, collaborative operation of a group of unmanned vehicles attracts much attention for effective response in disaster environments. In particular, mission planning is crucial for an effective collaboration of multiple heterogeneous vehicle systems. This study presents a mission planning algorithm and its application procedure in disaster situations. In general, disaster response missions such as search, rescue, and oil spill tracking are complicated in nature and come in various forms. Therefore, the mission needs to be broken down into simpler tasks that are more readily achievable to autonomous vehicles without human intervention. This study also presents a set of algorithms for efficient initial search and task allocation. The performance and feasibility of the proposed methodologies are evaluated with numerical simulations.