This chapter describes the prospects for reducing the impact of aviation on the environment through operational changes, new airframe and engine technologies, and biofuels. The focus is on the in-flight impact on the environment with particular emphasis on climate change impact. Examples of operational changes include optimized profile descents, reduced vertical separation, multistage long-distance travel, formation flight, and large aircraft for short ranges. New airframe technologies described include active laminar flow control and novel aircraft configurations such as the double bubble and the blended wing-body. Various possible approaches to improve the efficiency of jet engines are described as well as means of reducing nitrogen oxide emissions, such as lean premixed combustion. Prospects for large-scale use of biofuels are discussed and the technical path that should be taken in developing and adopting alternative jet fuels is presented.