By Bjorn Fehrm

June 13, 2025, ©. Leeham News: We do a Corner series about the state of developments to improve the emission situation for Air Transport. We try to understand why development has been slow.

We have examined different ways to lower global warming over the course of the series. Over the last weeks, we have summarized what practical results we can expect from the different alternatives we have to reduce global warming from Air Transport. We looked at the following alternatives:

How do the initiatives on our lineup compare

Of the five different alternative ways to lower global warming, which is the most practical and can lead to a significant reduction in the warming effect in the short term, and which alternatives are more for the long term?

Let’s first single out the CO2 reduction ones and then compare these to the warming effect from Contrails.

The first CO2-reducing one is the one that occurs regardless of initiatives to lower emissions, the industry’s typical improvement in fuel consumption over time, Alternative 2. We can conclude that this was a powerful one, with a reduction in CO2 emissions between now and 2050 of around 600 million tonnes of CO2, compared to the scenario where there was no improvement in fuel consumption.

This shall be compared to today’s yearly emissions from Air Transport, where 300 million tonnes of Jet A1 fuel were burned during 2024, resulting in 950 million tonnes of CO2. It doesn’t mean we lower these emissions to 350 million tonnes, as we have growth in civil aviation. It means we have 600 million tonnes less of Jet A1-related CO2 emissions than we would have if there were no improvement in fuel consumption from new aircraft replacing old ones.

We shall compare this to our scenario in Alternative 1. In this scenario, we assume success in producing CO2 and NOx-emission-free airliners based on various Turboprop replacement projects. These projects can replace the existing 19, 30- to 50-seat, and 70- to 100-seat turboprops currently in the market.

We assume that the 19- and 30-to-50-seat projects will result in Entry Into Service (EIS) of aircraft from 2030. The replacement of 70 to 100-seat turboprops starts in 2040 when we assume Airbus delivers its ZEROe fuel cell-based hydrogen airliner.

In total, these projects would have reduced Jet A1 consumption between now and 2050 by 7.2 million tonnes, equivalent to approximately 23 million tonnes of CO2.

Alternative 3 involves the gradual mandating of increased SAF (Sustainable Aviation Fuel) blends in the EU, which would result in an improvement of 106 million tonnes by 2050.

Finally, we have of the CO2 emission reducing alternatives, the effects of ETS on air transport, Alternative 4. This is more difficult to quantify, as the reductions done by individual airlines are not researched and extrapolated in a convenient manner.

We had the figure of air transport contributing 50 million tonnes of CO2 in the EU and affiliated states, and research had shown a typical 7 to 10 percent reduction from an industrial sector enrolled in the EU ETS versus not. This would then mean a three to five tonne reduction in CO2 emissions from the EU ETS for air transport.

CO2 emission reduction summary

To summarize, we have from the CO2 reduction initiative the following reduction in CO2 emissions by 2050:

Figure 2. The effect by 2050 of the different CO2 reduction alternatives we have examined. Source: Leeham Co.

We shall compare the warming reduction effects of these reductions to the effect of NOx, other sources, and avoiding warming contrails in the next Corners, as this is an analysis that requires some thought and discussion.