text: The engineering options for mitigating the climate impacts of aviation.
  Aviation is a growing contributor to climate change, with unique impacts due to the altitude of emissions. If existing traffic growth rates continue, radical engineering solutions will be required to prevent aviation becoming one of the dominant contributors to climate change. This paper reviews the engineering options for mitigating the climate impacts of aviation using aircraft and airspace technologies. These options include not only improvements in fuel efficiency, which would reduce carbon dioxide (CO2) emissions, but also measures to reduce non-CO2 impacts including the formation of persistent contrails. Integrated solutions to optimize environmental performance will require changes to airframes, engines, avionics, air traffic control systems and airspace design. While market-based measures, such as offset schemes and emissions trading, receive growing attention, this paper sets out the crucial role of engineering in the challenge to develop a 'green air traffic system'.