Post Macondo, industry publications have discussed the equipment, connections, and interfaces needed for capping and containing a blowing subsea well, but they give little insight into developing a well-specific subsea-capping contingency plan. The planning process described here, which has been used successfully on multiple projects and source-control drills, involves assessing the feasibility of deploying a capping stack from a floating vessel, the weight and stability of the capping stack to overcome the force of the blowout jet, and dynamic flow simulations of closing the capping stack outlets without loss of well integrity. This process not only assesses the feasibility, complexity, and risk exposure of the capping operation, but may also justify further planning, studies, or expenditure.