How do airlines design their routes?

What new opportunities does the corona crisis offer?

When it comes to fast global freight transport and long-distance travel, the plane is usually the means of transport of choice - even if it has so far been considered less ecological. However, this could change soon. After the corona lockdown, the cards in the aviation industry will be reshuffled. In addition, the climate issue has established itself in the minds of consumers. With this in mind, the airlines would do well to work flat out on the vision of climate-neutral flying.

After the corona shutdown, airlines have the opportunity to make cargo and passenger flights much more climate-neutral than before.


Aviation shame, cheap flight tickets, kerosene tax, number 1 climate killer: the aircraft is not doing exactly well in the current climate debate. In the public debate, it is considered the most climate-damaging means of transport. For example, anyone who flies from Frankfurt to Sydney and back uses roughly the same amount of CO2 like the “average German” in a whole year - including car trips, heating costs and food. Nevertheless, global air traffic has always recorded permanent growth and reached another record high in 2019. In the global transport of goods, the sustained expansion of world trade in particular has intensified the rapid increase in air freight volumes in recent decades. Aviation logistics are characterized by short transport times over long distances, fast cargo handling or rapid forwarding by Road Feeder Services. Since the logistics chains in air freight transport are also very precisely organized, air freight is an ideal method of transporting goods with a high need for urgency. Flight plans that are meticulously adhered to ensure that shipments can be precisely timed. The overall logistical concept is therefore less prone to failure than with other freight methods. However, the disadvantages of air freight include the high transport costs due to the kerosene consumption of airplanes. For a comparable transport service, an airplane consumes about twelve times more fuel than a seagoing ship.

Covid-19 - a warning signal from nature?

“Flights” do not pass the earth without a trace. Carbon dioxide, nitrogen oxides, water vapor, soot, sulphate and other particles, as greenhouse gases, contribute directly to global warming by increasing the anthropogenic greenhouse effect. What is special about this is that the climate-damaging gases are emitted at high altitudes at around 11,000 meters compared to all other means of transport. Temperatures of –50 ° C prevail at these altitudes, which is why ice clouds or contrails form. From this, in turn, artificial clouds develop, so-called cirrus clouds, which wrap around the earth like a tarpaulin, which means that the heat is stored and the earth heats up more quickly. In addition, the greenhouse gases sometimes have a contrary effect on the climate. Nitrogen oxides, for example, have a warming effect due to their contribution to ozone formation, but also have a cooling effect due to methane degradation. However, this does not result in a balance. The greenhouse gases only degrade very slowly, add up and ultimately worsen global warming. In addition, air traffic does not only have a local effect at the point of origin (e.g. through contrails or aircraft noise), but also globally, through the widespread distribution of pollutants in international passenger and goods traffic. The corona lockdown has now forced planes worldwide to return to the ground overnight and completely unexpectedly and is reshuffling the cards for the aviation industry. The future of our planet is in serious danger. In order to avoid an impending climate catastrophe, the ecological footprint of mankind must be drastically reduced in some areas. Also in the aviation industry.

Global climate polluters in comparison - air traffic really only causes 3% of the CO2 Emissions?

The worldwide CO2Emissions are made up of several segments. According to current estimates, air traffic contributes around 3% to anthropogenic, i.e. man-made climate change. Compared to the car with approx. 18% or the electricity and heating sector with approx. 42%, this is very little (Lufthansa, 2019). However, the validity of the numbers has to be questioned on closer inspection, since the focus in the assessment is on only one greenhouse gas, CO2, lies. This means that the fact that an aircraft is not just CO2 produced and thus significantly more pollutants and other factors have to be included in the calculation, are not taken into account.

The attempt to realistically and reliably calculate the ecological footprint of air traffic is proving to be a difficult undertaking. The Intergovernmental Panel on Climate Change (IPCC) has developed two approaches:

Method 1: Radiative Forcing Index (RFI factor) Method 2: Absolute Global Warming Potential (AGWP)

The RFI factor sets the radiative forcing of all air traffic effects in relation to the CO2. This cumulative value - usually between 1.9 and 4.7 - is then combined with the CO2Value multiplied. In order to integrate the longevity of the emissions, the composition of the atmosphere is examined at a fixed point in time and at the same time the total warming of the earth since the beginning of air traffic is included in the calculation (Federal Environment Agency, 2012).

The RFI factor does not only take into account the emitted CO2but all other pollutants that arise when kerosene is burned. In addition, the warming and cooling effects of the emissions are taken into account as well as their ratio. The longevity of the pollutants is also taken into account. This is essential because CO2 for example, only completely degrades in the atmosphere after approx.

However, short-lived emissions such as methane or nitrogen oxides are not taken into account. Method 2 is dedicated to this problem. When calculating the absolute global warming potential, both the disturbance intensity and the time factor are taken into account. Compared to the RFI factor, this method is more future-oriented. The warming effect of a greenhouse gas compared to the CO2 rated. Methane, for example, has a 21 times greater impact on the climate than CO2, but remains in the atmosphere less long. The exact calculation of the climate impact of the contrails is difficult. The problem here is that the intensity of the contrails occurs in different forms during the entire flight and depends on various factors, such as the weather situation or the altitude.

The ecological footprint of aviation is bigger than expected

When using the two calculation methods, the experts estimate the actual share of air traffic in the anthropogenic greenhouse effect at 5 to 8% and thus significantly higher than the often glossed over 3% (Atmosfair, 2020). The distribution of global pollutant emissions changes accordingly and the aircraft takes up a much larger space than originally shown.

Same route - Big differences in environmental friendliness

In comparison to other means of transport, flying is significantly damaging to the climate, but it is no longer possible to imagine the international movement of people and goods without it as a means of transport and transport. The airlines are now well aware of their climate responsibility. The aim is to increase energy efficiency and at the same time reduce fuel consumption and thus decouple transport performance and fuel consumption. The study on the Atmosfair Airline Index 2018 also shows that the differences between the individual airlines can be considerable. With some airlines the fuel consumption per passenger and kilometer is more than twice as high as with others - on the same route! The best values ​​are achieved by airlines that use modern aircraft that are adapted to the route. Efficient use of space with lots of seats, which enable optimal use of the passenger and cargo areas, give bonus points in the environmental friendliness ranking. Large areas of First and Business Class, on the other hand, worsen the balance sheet (Atmosfair Airline Index 2018).

In the end there is the vision of climate-neutral flying

But how can the ecological footprint of the airlines be reduced and ultimately perhaps even the vision of climate-neutral flying be realized? Some good news in advance: a lot has been done in the past and the foundation for climate-neutral flying has already been laid. Modern aircraft are significantly “cleaner” than their predecessor models. A new Airbus A350, for example, uses 25% less fuel than its predecessor models. The pollutant emissions are reduced accordingly. Continuous fleet modernization is therefore proving to be an important lever for airlines.

Synthetic fuels are also of great relevance, because they produce the significantly higher CO with around 90%2-Saving potential with it. With synthetic kerosene, CO is converted into an electrolysis process2 and water, crude oil is obtained, which is then further processed into kerosene. In flight operations, only the CO2 be emitted, which was previously taken from the atmosphere. However, this presupposes that the energy required to produce it is obtained from renewable energies. If all aircraft taking off in Germany were to be supplied in this way, the entire amount of electricity generated from renewable energies would have to be used in Germany in order to be able to produce sufficient fuel for German air traffic in a climate-neutral manner. Extracting carbon from the ambient air is very energy-intensive.

The problem is that the Sustainable Aviation Fuel (SAF) is not yet available in sufficient quantities and is therefore still too expensive for use in air traffic alone. In addition, while flying with SAF reduces the CO2- Solves the problem, but still pollutes the environment with its further effects. Here the altitude is crucial. Since the pollutants are considered critical especially in high air layers, relocating air traffic to lower altitudes would have positive effects. For example, 8,000 meters would be a suitable altitude at which there are no contrails, but safe flight operations are still possible. There, however, the air resistance is higher, which is why more fuel is required - but this is then CO2-neutral (Köhler, 2017).

By introducing a uniform European airspace - the so-called Single European Sky - waiting loops and detours would be avoided, which leads to a fuel and approx. 10 percent Europe-wide CO2Savings would result (Deutsche Lufthansa AG, 2019, p. 60).

An improved infrastructure on the ground would also have positive effects on the environment. By optimally combining air, rail and road transport, unnecessary environmental pollution would be avoided. In the future, travel to and from the airport could be conveniently carried out by ICE or car sharing (Deutsche Lufthansa AG, 2019, p. 61).

In addition, the aviation industry is the only mode of transport that takes part in emissions trading. Throughout the EU and internationally, the airlines acquire certificates in accordance with the CO2-Ceilings. The income then comes to CO2-compensating projects benefit. Using the example of the Lufthansa Group, around 62% of its CO2Emissions are offset (Deutsche Lufthansa AG, 2019, pp. 63–64).

Air passengers can use various compensation platforms on the Internet to share some of the inevitable CO2 offset your flight trip with a climate protection donation. This benefits projects that have been shown to have CO2 reduce and thus make a long-term positive contribution to the environment. In addition, Lufthansa passengers have the option of replacing fossil fuel with the synthetic and therefore more climate-friendly variant in a ratio of 1: 1 with their donation (Deutsche Lufthansa AG, 2019, p. 13).

Overall, there are some climate research projects that have been able to gather important knowledge about the negative effects of air traffic for some time. For this purpose, Lufthansa has regularly installed measurement laboratories in its passenger aircraft, which collect valuable data on the composition of the atmosphere at cruising altitude (Lufthansa, 2019 b).

Electric aircraft - the solution for short distances?

The measures outlined so far are promising, but only lead to a reduction in the ecological footprint. For example, if feeder flights to the hubs are served by electrically powered aircraft, critical pollutants such as CO2, Nitrogen oxides or fine dust can be avoided. Due to the associated weight problem with the batteries, however, they can only be used on short and medium-haul routes. Because around 70 kilograms of batteries are required for one liter of kerosene (Köhler, 2017). This could already reduce the share of global emissions by a large part.

Synthetic kerosene - the future for climate-neutral flying

On the long haul, there is no getting around synthetic kerosene. However, we still have to work on solutions to produce synthetic kerosene in large quantities so that it becomes economical for air traffic. The recently introduced hydrogen strategy of the federal government could remedy this problem. Investments are to be made in more production facilities for hydrogen, the “green fuel of the future”, and one of the greatest innovations in the field of climate protection and the energy transition is to be promoted. An important step towards a climate-neutral future and, thanks to the Corona crisis and the resulting economic stimulus package, passed earlier than originally thought (Tagesschau, 2020).

Aviation will be different

In addition to all the challenges for society, politics and the global economy, the pandemic gave nature a "breath of relief" for a brief moment and provided an insight into an almost pollutant-free environment. The aviation industry, on the other hand, couldn't have been worse. It suddenly fell to a level close to zero through no fault of its own. It is true that this offers a great opportunity to embark on a “new aviation” and finally to make the vision of climate-neutral flying a reality. At the same time, the airlines are in dire straits and are fighting for their existence. A healthy company like Lufthansa is catapulted into an existence-threatening crisis overnight and is dependent on government aid amounting to 9 billion euros. At the same time, the company suddenly recorded a surplus of more than 20,000 full-time positions (Warschauer, 2020). This is an unprecedented challenge even for Europe's largest airline.

What does the future of the aviation industry look like? Before the Corona crisis, hardly anyone would have expected such a cut - the volume of air traffic has always increased and, according to experts, should continue to grow in the next 20 years (Zeit Online, 2019). This was mainly due to the fact that ticket prices were getting cheaper and more and more people were using the plane as a means of transport. Hardly any aircraft are currently taking off. The future of many airlines is uncertain. Only one thing is certain: nothing will be the same as it was before the crisis (Koenen, 2020).

Slow return to normal? - Air traffic goes into the restart phase

Gradually the restart phase begins. The airlines are in a conflict between economy and ecology. There is a risk that environmental protection will fade into the background due to economic pressure and that all previous successes have been in vain. However, it should not be forgotten that climate issues have become firmly embedded in people's minds and will come back into focus over time.

In the end, the airlines have no other choice to get out of this crisis: In order to make their company competitive again, despite the financially very stressful situation, management must continue to work flat out on the vision of climate-neutral flying and the previous ones, solely on growth Reduce aligned strategic goals for sales and returns.

We have it in hand. Both the future of the aviation industry and that of our planet depend heavily on the lessons learned from the crisis (Nagels, 2020). And in many ways. The coronavirus should be understood as a kind of warning signal from nature and, especially with regard to aviation, should provide an incentive to make the vision of climate-neutral flying a reality so that one day you can get on an airplane with a clear conscience.


Atmosfair (2018). atmosfair Airline Index 2018.

Deutsche Lufthansa AG (2019). Balance. Sustainability Report 2019. 25th edition, Frankfurt am Main: Lufthansa Group Communications.

Köhler, R. (2017). Vision of environmentally friendly flying. Flying without polluting the environment.

Koenen, J. (2020). An industry on the ground: Corona crisis is reorganizing aviation.

Lufthansa (2019 a). Aviation - "Climate killer No. 1"? The fact check.

Lufthansa (2019 b).Around the world 85 times - for climate research!

Lufthansa (2019 c). Key climate policy messages.

Lufthansa (2020 a). Climate & Environment. Keeping an eye on the environment.

Tagesschau (2020). Hydrogen strategy. The stuff dreams are made of.

Federal Environment Agency (2012). Climate impact of air traffic. Current state of scientific knowledge about the effects of air traffic.

Warschauer, R. (2020). Corona consequences. Up to 26,000 Lufthansa jobs on the brink.

Lena Florian wrote her bachelor thesis at the IUBH International University under the title "The vision of climate-neutral flying - critical consideration of possible solutions for reducing the ecological footprint from the perspective of Deutsche Lufthansa AG". Hubert Vogl is a professor at the International University IUBH.