An aircraft is composed of systems that convert fuel energy to mechanical energy in order to perform work-the movement of people and cargo. Today, the fast-growing demand for air travel has outpaced the rate of improvement in the energy efficiency of aircraft systems. The increase in the total energy consumption and environmental impact of aviation necessitates a strategy to induce further technological and operational innovations to mitigate the increase in aircraft energy use and environmental effects. However, the uncertainty associated with the climate effects of jet engine emissions hinders further improvement to the energy efficiency of aircraft systems. Also the unique characteristics (e.g., trade-off between emissions species) of aircraft systems make it difficult to focus on abatement efforts. Based on a short review of how aircraft technology and operations relate to energy use and the future outlook for aircraft performance, energy use, and environmental impact, the key technology and policy issues related to improving the energy efficiency of aircraft systems are presented. Then, the drivers of technological change in aircraft systems are examined. Government regulation effects and industry characteristics as they relate to improvement of energy use are also presented. Based on these discussions, this paper provides insights on how to accelerate the induction of energy efficient, environmentally friendly innovations. (C) 2009 Elsevier Ltd. All rights reserved.