We present a comprehensive approach for assessment of long-term, fleet wide costs and benefits from advanced aircraft technologies in a variety of future scenarios. This effort requires an integrated methodology that combines system dynamics, network modeling and analysis, and fleet allocation optimization. The objective is to identify the levels and timing of technology enhancement that are most likely to advance the goals of greater efficiency in air transport while also reducing noise and emissions. Solution techniues for aircraft allocation problems are well developed. However, these allocation problems have not incorporated the time-varying dynamics in the air transportation system and the rage of environmental impacts at the fleet level. We present an approach and a tool that address this problem by integrating fleet allocation optimization with dynamics of demand (growth and price elasticity of demand), economic factors (fuel price and economic growth), and supply and demand relationship (aircraft order, delivery, and retirement of aging and inefficient aircraft). We analyze the impacts on noise and emissions of new technologies (aircraft and alternative jet fuel) and prospective environmental polices (incentives and constraints). We demonstrate the capability of this tool by exploring five scenarios on a network of 102 domestic airports in the U.S. Preliminary results along with their implications for decision making are presented and discussed.