Airplane pollution

Emissions from aviation are a significant contributor to climate change. Airplanes burn fossil fuel which not only releases CO₂ emissions but also has strong warming non-CO₂ effects due to nitrogen oxides (NOx), vapour trails and cloud formation triggered by the altitude at which aircraft operate. The climate impact of these non-CO₂ effects is comparable to that of aviation’s CO₂ emissions.

Before the COVID-19 pandemic, emissions from European aviation had been growing faster than any other mode of transport, and have more than doubled between 1990 and 2019. Aviation emissions went from 1.5% of all European emissions in 1990 to 4.7% in 2019. In 2025, emission levels exceeded pre-pandemic levels and 5% of European emissions. 

Aviation is set on a rapid growth path again. If this growth is unmitigated, aviation energy consumption could more than double (compared to 2019) by 2050 and in doing so, the sector could deplete its carbon budget to stay below 1.5°C of warming as soon as 2026.

Unlike the Kyoto protocol, which had specific emission targets only for developed countries, the Paris Agreement’s Temperature-based targets obliges  all countries  to have plans to limit global warming, and adopt “economy-wide” emission reduction targets. This “economy-wide” requirement means that despite there being no explicit reference to aviation – nor indeed are any other specific industrial sectors mentioned – the aviation sector remains covered by the agreement just like all other sectors.

To ensure compliance with the agreement, T&E calls for the inclusion of aviation emissions in countries’ climate plans under the Paris Agreement – known as Nationally Determined Contributions (NDCs). International emissions, like aviation’s CO₂ impact on international flights, are rarely included in NDCs even if legally, countries are obliged to, according to a prior analysis.Countries must include CO₂ and non-CO₂ aviation effects in the NDCs submitted ahead of the UN’s Climate Summit COP, held every year.  

Moreover, a legal analysis concluded that countries have a legal obligation to include non-CO₂ emissions - estimated to account for at least half of aviation’s climate impact - in their NDCs to comply with their commitment to the Paris Agreement. 

The UN’s aviation agency, the International Civil Aviation Organisation (ICAO) is set to adopt global measures, such as long-term emissions reduction goals and a global offsetting scheme (CORSIA) to reach net-zero carbon emissions by 2025. However, CORSIA is under particular scrutiny because to date, the offsetting mechanism has failed to stabilize aviation’s CO₂ emissions or  encourage the uptake of green technologies like SAF and zero-emission planes.  Moreover, a T&E analysis shows that CORSIA is an expensive distraction from climate measures that can have a real impact.

On top of CO₂, aircraft engines emit other gases – nitrous oxides (NOx), sulfur dioxide (SO2) and water (H2O) – and particulate matter (soot). When emitted at high altitudes, these emissions affect atmospheric physical and chemical properties. This results in an increase in greenhouse gases in the atmosphere, and the potential formation of persistent contrail cirrus. These artificial clouds act like a blanket that traps the Earth’s heat.

The consequence is a net warming effect, whose magnitude is estimated to be comparable to the warming caused by aviation’s CO₂ emissions.

Nevertheless, these effects are also short lived, meaning that acting against them would quickly reduce aviation’s contribution to global warming, scoring important wins in our fight against climate change.

Despite their considerable impact, no measures are in place at regional or global level to reduce aviation’s non-CO₂ climate impacts. As of 2025, the EU started monitoring non-CO₂ emissions on all flights departing from the bloc, with the view of potential legislation proposed by the European Commission in 2027.

Contrails cause a large share of aviation’s climate impact. They form when aircraft fly through cold and humid regions of the atmosphere.. But solutions exist to tackle the problem.

One solution could be to use cleaner fuels to reduce the amount of pollutants released in the air. Jet fuel with a large share of sulfur and aromatics is believed to increase contrail formation. One way to reduce the sulfur and aromatics content of fossil jet fuel is to hydrotreat it. Hydrotreatment is possible in existing refineries without significant additional costs, might lower contrail warming and would help millions of people living around airports.

Another promising solution to reduce aviation’s non-CO₂ climate impact is called contrail avoidance. It consists of small adjustments to flight paths, notably minor climbs or descents, to avoid those cold and humid atmospheric areas where contrails form. Simulations and real life tests have proven that this solution is very cheap and can substantially reduce contrail warming. 

In fact, contrail management could be the most effective lever to reduce aviation’s climate impact until 2050.

The first piece of evidence highlighting the importance of aviation’s non-CO₂ effects came from the UN’s Intergovernmental Panel on Climate Change (IPCC) back in 1999. Since then, a lot of excellent research has been carried out to better understand the effects of these emissions and how to tackle them.

The European Commission was first tasked with addressing the non-CO₂ emissions of flying in 2008, and commissioned a landmark report to the European Union Aviation Safety Agency (EASA). The report, published in 2020, analysed the latest available science, came to the conclusion that aviation’s non-CO₂ is an important problem, and proposed a number of mitigation measures.

However, these measures – and non-CO₂ effects in general – are hardly reflected in EU policy making. As part of the EU ETS,airlines started monitoring non-CO₂ emissions of inner-European flights in 2025. Europe should step up its efforts, as it is losing valuable time to mitigate most of the climate impact of aviation.

E-fuels such as power-to-liquid are a potential source of zero or lower carbon alternative fuels. E-kerosene (also known as e-SAF) is the only fuel that can be sustainably scaled up to reduce aviation’s climate impact. But they require enormous amounts of renewable energy and their environmental effectiveness depends on the source of the CO₂ required to produce the fuels. However, they do have the potential to significantly reduce emissions from the sector. T&E has developed a tracker with all the e-SAF plants being developed in Europe that you can find here. Read more on sustainable aviation fuels for planes and which airlines are buying and using them in T&E’s SAF Observatory ranking 77 airlines worldwide. 

Zero emissions aircraft, such as hydrogen or electric planes, can help decrease aviation emissions for shorter ranges, but they will need significant amounts of funding to be in operation in the mid 2030s. Read more on our views on new plane designs here.

As it is currently difficult to reduce emissions from this sector, flying less is the only way to reduce emissions in the critical decade before 2030. Flying less could mean taking a more sustainable mode of transport, such as train, or changing your destination to one which can be reached by less climate-intensive means. It could also mean teleconferencing instead of attending business meetings, or going on longer individual holidays, rather than several short, carbon-intensive, trips.

During the COVID-19 pandemic, the ease with which many employees adjusted to being home and flying less revealed that long-held ideas of the need to fly for work no longer stand. Reducing corporate travel is an easy way to cut aviation emissions. By reducing corporate travel to 50% of pre-COVID levels, we can cut CO₂ emission by as much as 32.6 MtCO₂ by 2030 in Europe, which is equivalent to taking 16 million polluting cars off the road.

Whatever the means of achieving it, demand reduction should not be a taboo subject. The sector’s emissions are soaring at a rate too high to ignore, and policymakers should not recklessly champion endless aviation growth while knowing how difficult it is to decarbonise the sector.

Emissions from flights represent the majority of an airport’s carbon footprint. Passenger flights departing Europe’s five biggest airports emit 53 million tons of CO₂ – the same as the entire Swedish economy. And a T&E study shows that 52 million people - more than 10% of Europe’s total population - live within a 20 km radius from the third busiest airports in Europe and are particularly exposed to ultrafine particles from aviation.

Many airports have announced plans to grow their air traffic. T&E analysis shows industry claims that more flights benefit the economy are often flawed. Building new terminals and increasing capacity is incompatible with Europe’s climate, air quality and health goals. Instead, airports should align their capacity with these policies, and ensure that air connectivity delivers genuine public value by focusing on quality rather than quantity. 

Airports can lead efforts through modulating airport charges to incentivise the use of cleaner aircraft and ensuring that suppliers of cleaner fuels have access to airport fuelling infrastructure. In this light, T&E analysis of European Investment Bank lending concludes that public finance should not support expansion of airport capacity, but rather enable and boost emerging zero-emissions airport infrastructure in line with Europe’s industrial strategy.