As of January 2012 aviation will be included in the European Union Emissions Trading Scheme. In a Directive adopted in 2008, the European Commission decided to make all flights to or from airports located in any of the 27 EU Member States subject to the scheme. Aviation will thus join the emerging global carbon economy. The sector accounted for some 4% of total carbon dioxide emissions from fuel combustion in the EU in 2008, and 13% of CO2 emissions from all transport sources, but its emissions could increase by an average 2.5% a year in the medium term due to strong growth trends in air traffic. The aviation sector has identified several ways of decoupling its emissions from traffic growth, ranging from improved fuel use efficiency to the development of sustainable alternative jet fuels. Its inclusion in an emissions trading scheme is likely to further stimulate its emissions reduction efforts. This chapter highlights the main facts, figures and trends related to aviation greenhouse gas emissions. It then describes the principles for the inclusion of aviation in the European Union Emissions Trading Scheme and assesses emissions projections and anticipated demand for aviation allowances up to 2020. Finally, it reviews the range of existing and future options for reducing CO2 emissions in the aviation sector based on three main levies: an active air transport demand management policy, an increased efficiency of fuel use through technology, operations, or infrastructure improvements, and a lower carbon content of jet fuels.