The main pollutants emitted by aircraft engines in operations are carbon dioxide (CO2), nitrogen oxides (NOX), sulphur oxides (SOX), unburnt hydrocarbons (HC), carbon monoxide (CO), particulate matter (PM) and soot (Figure 1.8). This section provides trends in full-flight emissions of all flights departing from EU28 and EFTA airports.

CO2 and NOX emissions are continuing to grow

According to the data reported by Members States to the United Nations Framework Convention on Climate Change (UNFCCC), the CO2 emissions of all flights departing from EU28 and EFTA increased from 88 to 171 million tonnes (+95%) between 1990 and 2016 (Figure 1.9). In comparison, CO2 emissions estimated with the IMPACT model reached 163 million tonnes (Mt) in 2017, which is 16% more than 2005 and 10% more than 2014. Over the same period, the average fuel burn per passenger kilometre flown for passenger aircraft, excluding business aviation, went down by 24%. This has reduced at an average rate of 2.8% per annum between 2014 and 2017. However, this efficiency gain was not sufficient to counterbalance the increase in CO2 emitted due to the growth in the number of flights, aircraft size and flown distance. Future CO2 emissions under the base traffic forecast and advanced technology scenario are expected to increase by a further 21% to reach 198 Mt in 2040. The annual purchase of allowances by aircraft operators under the EU Emissions Trading System (ETS) since 2013 resulted in a reduction of 27 Mt of net CO2 emissions in 2017, which should rise to about 32 Mt by 2020.

NOX emissions have followed a steeper upwards trend than CO2 in recent years (Figure 1.10). They increased from 313 to 700 thousand tonnes between 1990 and 2016 according to the Convention on Long-Range Transboundary Air Pollution (CLRTAP) data from the UN Economic Commission for Europe, and by 25% between 2005 and 2017 according to estimates from the IMPACT model. Unlike the CO2 trend, current predictions indicate that the advanced engine NOX technology scenario could lead to a downward trend after 2030. However, NOx emissions would still reach around 1 million tonnes in 2040 under the base traffic forecast (+45% compared to 2005).

Aviation emissions in context
In 2016, aviation was accountable for 3.6% of the total EU28 greenhouse gas emissions and for 13.4% of the emissions from transport, making aviation the second most important source of transport GHG emissions after road traffic [17]. Greenhouse gas emissions from aviation in the EU have more than doubled since 1990, when it accounted for 1.4% of total emissions. As emissions from non-transport sources decline, the emissions from aviation become increasingly significant [10]. European aviation represented 20% of global aviation’s CO2 emissions in 2015. Aviation is also an important source of air pollutants, especially of nitrogen oxides (NOX) and particulate matter (PM). In 2015, it accounted for 14% of all EU transport NOX emissions, and for 7% of the total EU NOX emissions. In absolute terms, NOx emissions from aviation have doubled since 1990, and their relative share has quadrupled, as other economic sectors have achieved significant reductions. The carbon monoxide (CO) and oxides of sulphur (SOX) emissions from aviation have also gone up since 1990, while these emissions from most other transport modes have fallen [18].

It should be noted that the aviation sector is not fully comparable to other sectors of the economy, as emissions reductions can be more difficult to achieve in aviation. This is partially due to the relatively long lifespan of aircraft, which could remain in operation for 25 years or more. Cap-and-trade systems, as well as offsetting schemes, allow to compensate emissions from aviation through reductions achieved more easily in other sectors. However, aviation will need to deliver more in-sector emissions reductions.


Due to fleet renewal, emissions of HC, CO and PM have been relatively stable between 2005 and 2014. However, PM emissions are expected to increase over the next twenty years if engine technology remains as it is today (Table 1.3).