Climate protection report

1. The impact of aviation on the climate

The demand for air transport is growing all over the world – and so are the emissions that are affecting the climate. In addition to the CO2 emissions it produces, the aviation sector is also responsible for other emissions resulting from the combustion of fuel at high altitudes. These emissions also have an impact on our climate, as they can contribute to the formation of clouds and other greenhouse gases. However, there are a number of approaches to reducing these effects – for example, by changing flight routes or using sustainable aircraft fuels.

According to the Intergovernmental Panel on Climate Change (IPCC), the total impact of aviation on the climate is 3 to 5 percent and depends on a range of factors: The type and volume of emissions, weather conditions, the time of day and where the emissions are released, the length of time they remain in the atmosphere and their geographical dispersion. The emissions generated when kerosene is combusted that are of relevance for the climate include not only carbon dioxide and water vapour, but also nitrogen oxides (NOX), sulphur dioxide (SO2) and soot particles. As a result, vapour trails (cirrus clouds) can form behind the aircraft if it is flying at a very high altitude in very cold conditions. The emissions stated above have an impact on the atmospheric concentrations of carbon dioxide (CO2), ozone (O3), methane (CH4), water (H2O) and aerosols.

While the impact of carbon dioxide on the climate has been the subject of extensive scientific research, further research is still needed, for example, in order to estimate the effects that contrails, cirrus clouds and nitrogen oxides have on the climate.

Given that CO2 has a particularly long life compared to other emissions, the focus in reducing the impact of aviation on the climate is on cutting CO2 emissions especially – but without neglecting the others.

Aviation’s share of global CO2 emissions

International aviation currently accounts for 3.01 percent of global CO2 emissions. In order to continually reduce these emissions, the sector is investing in more energy-efficient aircraft, compensating for growth-related CO2 emissions and pushing ahead with the development of sustainable, carbon-neutral fuels.

In the EU, air travel within the respective member states accounted for 0.76 percent of all CO2 emissions in the EU in 2018. In Germany, domestic German flights accounted for around 0.3 percent of all emissions.

2. Aviation’s international climate protection strategy

In 2009, airlines, aircraft manufacturers, air navigation service providers and airports worldwide agreed a climate protection plan: to increase fuel efficiency by 1.5 percent per year; to achieve carbon-neutral growth in air travel by 2020; and to halve net CO2 emissions by 2050 compared to 2005 levels.

Already today: Increase efficiency – reduce CO2 increase

Reducing the specific energy requirements of aircraft will cut fuel consumption and, in turn, CO2 emissions. The measures designed to achieve this improvement include technical innovations by aircraft and engine manufacturers, optimally coordinated operational processes on the ground and in the air, and implementation of the Single European Sky (SES).

The target: fly carbon-neutral

In order to be able to fly carbon neutral in the long term, we need to see the development of new airplanes, alternative fuels and engines, combined with the political support to make their use commercially viable.

On the way to the target: offsetting carbon growth

As global air traffic continues to grow, the reduction in specific fuel consumption is not enough to stop the increase in CO2 emissions. Therefore, at the UN level, the international CO2-offsetting system CORSIA was adopted by the International Civil Aviation Organization, ICAO. As part of CORSIA, growth-related CO2 emissions of international flights will be compensated by financing carbon offset projects from 2020 onwards. In Europe, air transport has already been included in emissions trading since 2012 and has been growing in carbon-neutral terms since then.

3. Increasing efficiency through modern technology

Thanks to modern technology, air transport is becoming increasingly efficient from an ecological point of view. This is achieved by using less fuel-intensive aircraft, more energy-efficient airport buildings and optimised ground handling procedures.

Modern aircraft are consuming less and less fuel. As a result, aviation is successfully keeping the increase in kerosene consumption and CO2 emissions lower than the growth in traffic: While air traffic in Germany has more than tripled since 1990, kerosene consumption has risen by just 123 percent during the same period.

This decoupling of kerosene consumption from traffic growth has been achieved primarily by measures to increase energy efficiency.

Consumption in passenger traffic is declining

By modernising their fleets, i.e. replacing old aircraft with new, more energy-efficient models, German airlines have succeeded in cutting specific CO2 emissions by 43 percent since 1990. Since fuel costs account for up to 25 percent of operating costs and a single tank of fuel for an Airbus A380 costs more than 100,000 euros, it is in the airlines’ own interest to invest in greater efficiency.

Factors for consumption: distance and load factor

The consumption per passenger for air traffic depends on, among other things, the passenger load factor, the flight level and distance flown. Charter flights use, on average, less kerosene per person because long-term planning and booking generally mean a higher passenger load factor than scheduled flights.

On short-haul flights, consumption during take-off and landing is relatively higher than on medium or long-haul flights – the lower flight altitude also causes more drag on short-haul flights and thus higher consumption.

Consumption of the cargo fleet decreases

German cargo aircraft are also more efficient than ever: expressed in terms of passengers, the Lufthansa Cargo fleet only uses 1.87 litres per 100 kilograms of weight (equivalent to one passenger with luggage) over 100 kilometres. A freighter consumes less fuel per 100 kilograms of weight than a passenger aircraft because the space available can be utilised more efficiently.

42 billion euros for 196 more fuel-efficient aircraft and less CO2

Reducing the fuel consumption of an aircraft, and thus its carbon footprint, requires a multifaceted approach. Key factors are propulsion systems, aerodynamics and weight. Technical innovations mean that fuel consumption is reduced by up to 25 percent with each new generation of aircraft. Therefore, the most effective investments are in new aircraft. As a result, German airlines have ordered a total of 196 more fuel-efficient aircraft worth 42 billion euros by 2027. It is an effective combination of economy and ecology, given that fuel costs account for up to 25 percent of an airline’s overall operating costs.

ICAO CO2 standard

To ensure that efficiency continues to grow in the future, the International Civil Aviation Organisation (ICAO) has introduced a new standard that sets CO2 limits to ensure that aircraft do not exceed a certain level of CO2 emissions. It was drawn up between various governments, industry and observers from environmental protection organisations and will apply to new aircraft models subject to certification as of 2020, and to all aircraft models that are already certified from 2028.

Curved wingtips

Some birds spread their wingtips upwards during flight because this reduces air resistance. The condor is a particularly striking example of this. The curved tips at the ends of aircraft wings work on the same principle. They reduce air turbulence, thereby saving fuel: by an average of up to five percent.

Particularly smooth wing surfaces (laminar wings)

Aircraft lift off the ground because uplift is generated by the wings. This is created by the air flowing around them. The air flow should be as uniform as possible – i.e. free of turbulence. The term laminar is used to describe this uniform flow of air. Laminar airflow is disrupted by turbulence, which can be caused by ridges on the wings, for example. These increase drag and the aircraft consumes more kerosene. New wing shapes incorporating laminar properties are designed to reduce turbulence as much as possible. Potential fuel savings of up to 5 percent show that this is where it pays to carry out ongoing research and development.

More efficient engines

The Trent XWB built by Rolls-Royce is one of the most efficient large aero engines in the world. It is used on the Airbus A350-900, which is already part of the Lufthansa fleet. One of the factors that ensure greater efficiency is a more compact design, which reduces the weight of the high-pressure compressor by 15 percent. The high bypass ratio of 9.6 to 1, in particular, has a positive effect on fuel consumption. The Trent XWB is 15 percent more fuel-efficient than its predecessors.

Aircraft parts from a 3D printer

The aircraft industry is utilising the advantages of 3D printing to produce particularly lightweight components. Each kilogram of weight saved reduces CO2 emissions by up to 25 tonnes over the entire life cycle of an aircraft. Aircraft parts from a 3D printer weigh up to 55 percent less than conventional components and reduce raw material consumption by up to 90 percent.

Fuselage and wings made from composite materials

Aircraft manufacturers are increasingly using ultralight composite materials (carbon-fibre reinforced plastic – CFRP) in the manufacture of fuselages and wings. While the Airbus A380 still has a 22 percent share of CFRP, the Boeing 787 already has a 50 percent share. At 53 percent, the modern A350 has an even higher share. Boeing’s new 777X will contain a similar percentage. Composites are 20 percent lighter than aluminium and contribute to the aircraft consuming less fuel and therefore emitting less CO2.

Carbon footprint at German airports

Airports and airlines regularly compile statements on the carbon emissions generated by their operations.

These take into account, for example, aircraft emissions during take-off, landing, while on the ground and during handling, as well as the CO2 released as a result of supplying energy to airport buildings. In this connection, the Greenhouse Gas Protocols classify carbon emissions into three categories (scopes).

Using sustainable technologies at airports

The German airports have joined the initiative by the European airport association ACI to become carbon neutral by 2050 and have already succeeded in cutting their CO2 emissions by 29 percent between 2010 and 2019. This is due, among other things, to the use of renewable energy such as solar and wind power as well as the optimisation of ground processes and specific airport facilities. The construction of sustainable airport buildings has further decreased energy consumption.

Moreover, there are already more than 1,800 (hybrid) electrically powered vehicles in use at German airports today. If this development continues, this figure could be as high as 10,000 in the future.

Fewer emissions at the airport

To reduce the need for aircraft to switch on their auxiliary power units (APU) at Munich Airport, (1) pre-conditioned air (PCA) systems have been installed at all parking positions close to the buildings at Terminal 1, Terminal 2 and the T2 satellite terminal. These cool, ventilate or heat (2) the aircraft cabin during ground handling as well. In Munich, a total of 64 systems are available, which can reduce CO2 emissions by up to 23,500 tonnes per year.

Supplying ground power to parked aircraft also reduces emissions at airports. Nowadays, almost all airports provide stationary or mobile aggregates (3). This can decrease the amount of fuel required to operate the APUs and as a result, corresponding CO2 emissions can be cut by around 90 percent.

Modern building technology reduces CO2 emissions

The new satellite building at Munich Airport’s Terminal 2 also sets new environmental standards. The building was designed together with Lufthansa as a “Green Satellite”, with CO2 emissions at least 40 percent lower than those generated by the existing terminal buildings. Among other things, a special climate-control facade ensures a high level of efficiency. At Dusseldorf Airport, some parts of the building are equipped with a temperature control system that is guided by the weather forecast. This technology will also be installed in other airport buildings in the future.

4. Organising climate protection in an integrated manner

As well as using technology to increase efficiency and consequently cut carbon emissions generated by aviation, optimised air traffic control processes and shifting traffic to rail also play a role.

The number of domestic flights in Germany is falling

Thanks to larger aircraft on domestic routes and more attractive rail connections, domestic flights have been reduced by 17 percent since 2004. Moreover, most domestic air traffic in Germany now consists solely of flights over longer distances.

Domestic flight connections are not only important for business travel, but also for the functioning of the entire German air transport system: This is because a share of domestic passengers fly to a German hub airport from where they continue on their journey to an international long-haul destination.

Shifting domestic air traffic to the railways

However, when it comes to deciding whether to fly or take the train within Germany, it is not the length of the route or the price that is crucial, but usually the travel time. A rail journey time of around three hours has emerged as a significant threshold for shifting demand from air to rail. Where this is the case, it has been possible to discontinue flight routes as a result of attractive rail connections, for example between Hamburg and Berlin, Cologne and Frankfurt, Berlin and Nuremberg or Cologne and Stuttgart. In addition to these routes, flights from Berlin to Bremen and Dortmund as well as from Hamburg to Leipzig have been discontinued.

Reducing specific fuel consumption with high load factors

Energy efficiency can also be increased when operating an aircraft. With this in mind, airlines are working to increase load factors and improve routing together with air traffic control. Compared to the average car load factor of around 30 percent (equivalent to 1.5 people) and German long-distance trains at 56.1 percent, on average, German air travel achieved a high load factor of 83.1 percent in 2019. This even exceeds the global figure of 82.5 percent. As a result, the specific fuel consumption per passenger has also been significantly reduced.

Enhanced processes on the ground

Airport Collaborative Decision-Making (A-CDM) is a European concept with the aim of improving ground processes at airports. This is because only a seamless flight is an energy-efficient flight.

This formula is based on complex processes and coordination between all system partners involved in the flight, such as airport operators, airlines, handling companies and air traffic control. An aircraft waiting on the ground needs energy because the engines, electronics and air conditioning have to be kept running. The faster an aircraft can take off again, the less energy it consumes at the airport – and the higher the efficiency in terms of transport performance.

Less energy consumption thanks to optimised descent

German air traffic control (DFS) is continuing to develop CDO (continuous descent operations) in close cooperation with German airlines. The procedure is supplemented with what is known as “late descent”, which the pilot specially calculates and initiates after leaving cruising altitude following clearance by the air traffic controller. In this way, the aircraft travels at high altitudes for as long as possible before approaching the airport in a steady descent.

This is because the higher an aircraft flies, the less fuel it consumes. Past simulations have shown that savings of up to 85 litres per flight can be achieved. What is more, CDO also cuts noise emissions in the vicinity of the airport. The CDO procedure is already in use at airports in Hamburg, Hanover, Leipzig, Dusseldorf, Cologne/Bonn, Frankfurt, Nuremberg, Stuttgart, Munich and Berlin.

Reducing contrails

During medium and long-haul flights, aircraft reach an altitude of over ten kilometres when in cruising flight. At this altitude, artificial clouds form under certain conditions. In certain circumstances, these contrails can develop into cirrus clouds. Depending on the situation, cirrus clouds can either heat up or cool down the Earth’s atmosphere. The contrails, and hence also cirrus clouds, can be avoided by diverting aircraft away from the areas where they form. However, this in turn leads to higher CO2 emissions. The aviation industry and scientific researchers are currently working together on how these findings could be implemented during flight operations.

Ongoing development of European airspace

Fuel savings could be achieved in European airspace by means of cross-border and more direct flight routes. The European Commission states a savings potential of 10 percent in the context of the “Single European Sky” programme. For European states, however, organising and controlling their own airspace is still a key part of their sovereignty. This results in detours as well as avoidable emissions and costs in the billions. Further modernisation of air traffic management within European airspace is essential in order to harness the considerable potential for reducing aviation-related carbon emissions. To this end, cross-border cooperation must be improved by modernising the EU’s airspace architecture, especially by standardising the division level between upper and lower airspace. Standardisation and automation of air traffic control services and greater flexibility in the deployment of controllers are also required. The objective is to organise traffic more efficiently in the recently established nine Functional Airspace Blocks (FABs).

German air traffic control’s contribution to climate protection

In recent years, German air traffic control (DFS) has ensured optimal routings so that aircraft are not forced to take as many detours,

thus enabling a 31 percent reduction in the average deviation from an aircraft’s ideal flight path in Germany – down from 5.5 km in 2010 to 3.8 km in 2019. If the kilometres saved in this way on all flights were added together, it would be equivalent to an aircraft circumnavigating the globe 141 times.

Ensuring optimal routings has reduced carbon emissions by some 71,000 tonnes in 2019 alone.

5. Innovative concepts for sustainable aviation

Alternative fuels and electric power are playing an increasingly crucial role in the aviation sector. While alternative fuels can already be used in conventional engines, electric propulsion systems require completely new aircraft concepts.

Sustainable aviation fuels facilitate carbon-neutral flights

However, in spite of increasing efficiency, the long-term target of reducing carbon emissions generated by aviation to zero can only be achieved if fossil kerosene is replaced by renewable fuels. There are a number of approaches in this context: one of the most environmentally friendly ways is an electricity-based fuel.

With the help of electricity produced by renewable means, water is broken down into its components oxygen and hydrogen and the CO2 required for this process is then extracted from the atmosphere. In a complex process, hydrogen and CO2 are subsequently combined to form a synthetic crude oil, which is then converted into kerosene.

If an aircraft then flies on this fuel, it emits the same amount of CO2 into the atmosphere that was previously extracted from it for the production of the fuel and, on balance, travels on a carbon neutral basis. The resulting fuel is interchangeable and miscible with conventional kerosene, so it can be used while maintaining all quality and safety requirements and utilising the existing infrastructure. Employing alternative aviation fuels also have a positive effect on the impact aviation has on the climate. The number of contrails falls because they contain fewer particles.

The use of alternative fuels in regular flight operations cannot be achieved overnight, since they are not available in sufficient quantities at the moment and are still too expensive. Nevertheless, the technology for the production and use of synthetic fuels has been tried and tested and found to work. The question of whether and when such fuels can be used is therefore essentially not one of technical feasibility, rather one of an overall energy policy framework.

Electric propulsion systems facilitate new aircraft concepts

Prototypes such as the E-Fan developed by Airbus, the Sun Flyer 2 by Bye Aerospace or even the recently tested flying taxi by Lilium show that it is possible to fly on a small scale with only an electric propulsion system. However, conventional propulsion systems will remain essential for large-scale commercial passenger traffic in the years ahead. By contrast, hybrid-electric aircraft seating up to 100 passengers could take to the skies as early as 2030  – for example, on shorter, highly frequented routes such as Berlin – Cologne/Bonn and in regional air transport.

The major advantage of hybrid-electric engines is that, unlike conventional engines, power generation can be concentrated at one point in the aircraft’s fuselage, from where it can supply power to a number of propellers.

The power required could be generated by a gas turbine, fuel cell or battery, for instance. The E-Thrust concept developed by EADS is one such hybrid system. In this case, the aircraft is not powered by conventional turbines, but by electricity-driven propellers. The required electricity is generated by a gas turbine in the rear of the aircraft, which can be powered by sustainable aviation fuel.


6. Carbon pricing mechanisms in aviation

As long as there are no technical possibilities to fly on a carbon neutral basis, mechanisms have to be used to offset the inevitable carbon emissions generated by aviation by reducing CO2 in other sectors.

European Union Emissions Trading System (EU ETS)

Intra-European air transport has been included in emissions trading since 2012 and pays for a substantial part of the emissions it produces. Using this mechanism will ensure that emissions from all sectors of the economy included in the emissions trading system are cut by 43 percent on 2005 levels by 2030. The fixed upper limit (cap) on CO2 had already fallen by an annual 1.74 percent by 2020. Starting in 2020, it will be then lowered by a further 2.2 percent per year.


At the same time, the certificates allocated free of charge to the aviation sector will be reduced by 2.2 percent annually. German airlines now have to buy CO2 certificates for 62 percent of the emissions produced by their intra-European flights. In so doing, they finance investments aimed at reducing the carbon emissions of all the economic sectors included.

International carbon pricing using CORSIA

The emissions trading mechanism was not enforceable for global air transport in the international community. Instead, a separate CO2 pricing scheme was agreed for international aviation at the UN level in 2016: Based on 2019 emissions, the internationally coordinated CORSIA (Carbon Offsetting and Reduction Scheme for International Aviation) CO2 compensation system regulates the pricing of carbon emissions for international flights and applies worldwide. International aviation has expressed its strong support for the introduction of this system. With CORSIA, as with emissions trading, emissions that cannot currently be avoided in one sector – in this case aviation – are reduced in another sector. It works like this:

Under CORSIA, airlines have to pay for their growth-related emissions. These funds are then used to finance climate protection projects certified by the ICAO. This means that, on balance, no additional CO2 is emitted.

Individual climate offsets

Airline passengers already have the option to offset the climate impact of their respective flight today. However, not very many passengers have made use of this option to date. For this reason, German airlines are increasingly incorporating offers to offset carbon emissions or to promote sustainable environmental projects into their booking procedures. This is to raise passengers’ awareness of the offers available. Many airports also offer the opportunity to offset carbon emissions through various providers. For example, the costs for the voluntary offsetting of flights from Berlin to Cologne are 3 euros, 7 euros from Berlin to Majorca and 27 euros from Berlin to New York (scheduled economy flight at myclimate).

7. Conversion factors

1 kg kerosene emits 3.15 kg CO2
0.4 litres of kerosene emit 1 kg CO2

4 litres per passenger per 100 km
are equivalent to approx. 100 grams of CO2
per passenger per kilometre

0.2 litres per tonne per kilometre
is equivalent to approx. 500 grams of CO2 per tkm

Energy density
1 kg kerosene ≙ 42.8 MJ (megajoules)
1 MJ ≙ 0.023 kg kerosene

1 l kerosene ≙ 34.24 MJ
1 MJ ≙ 0.029 l kerosene

1 kg kerosene ≙ 11.9 kWh
1 kWh ≙ 0.084 kg kerosene

Mass density
1 l kerosene = 0.8 kg kerosene
1 kg kerosene = 1.25 l kerosene

1 l = 0.264 US gal liq (US gallons)
1 US gal liq = 3.785 l

1 l = 0.00629 bl (barrel)
1 bl = 159 l

Freight and passengers
1 passenger incl. luggage is equivalent to 100 kg
≙ 1 TU (transport unit)

1 tonne of freight is equivalent to ten
passengers incl. luggage ≙ 10 TU
(transport units)

1 m = 3.28 ft (feet)
1 ft = 0.3048 m

1 km = 0.62 mi (miles)
1 mi = 1.61 km

1 km = 0.54 NM (nautical miles)
1 NM = 1.852 km
1 NM = 1 sm (sea miles)

100 km/h = 54 kn (knots)
1 kn = 1 NM/h = 1.852 km/h

1 MJ = 1,000,000 J = 106 J

1 PJ = 1,000,000,000,000,000 J = 1015 J

Editors’ note: At the time of writing, the coronavirus has been spreading around the world, causing profound changes in many areas of life, including aviation: Global air traffic almost came to a complete standstill in the spring of 2020, and it will take years to recover. However: The reporting period covers 2019 and earlier. Accordingly, this report only reflects statistics and developments prior to the pandemic.


Private: Julia Fohmann-Gerber
Press Spokesperson
+49 30 520077-116
More information
Climate protection report 2020