The U.S. Navy is currently designing the next generation aircraft carrier, the CVN 21. This class of carriers will use the same basic hull form as the current Nimitz class but will include a substantial redesign of the interior of the ship for improved weapons handling and stores management functions. It will also incorporate several new technologies including a new propulsion system and new aircraft launch and recovery systems. These improvements not only will increase the operational capability of the ship but also are anticipated to lower the ship's manpower requirements and maintenance costs. Under current force modernization plans, new ships of the CVN 21 class will be introduced every four or five years as the ships of the Nimitz class reach the end of their planned 50-year operational life. Under this strategy, Nimitz class carriers will be operating for over 50 more years and it will take decades to transform the aircraft carrier fleet to ships of the new class.On the basis of some preliminary calculations that appeared promising, RAND proposed to the Program Executive Office (PEO) for Aircraft Carriers an examination of a way to accelerate the transformation of the carrier force: replacing Nimitz-class carriers as they reach mid-life instead of refueling them. In this report we identify specific fleet management options for building new instead of refueling, and we evaluate their advantages and disadvantages. This report should be of interest to Navy and Office of Secretary of Defense planners examining fleet modernization options, especially those organizations addressing the costs of alternative force structure options.