Aircraft data from five levels (900 to 180 mb.) are used to depict the structure of a mature hurricane. Horizontal analyses, vertical cross sections, and various budgets, which have been prepared from the research flight data only, are presented. New estimates of the drag coefficient under hurricane conditions are derived from a different formulation utilizing the momentum budget in the inflow layer. Abstract Aircraft data from five levels (900 to 180 mb.) are used to depict the structure of a mature hurricane. Horizontal analyses, vertical cross sections, and various budgets, which have been prepared from the research flight data only, are presented. New estimates of the drag coefficient under hurricane conditions are derived from a different formulation utilizing the momentum budget in the inflow layer.