By Bjorn Fehrm

May 9, 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.

Since we started in October last year, we have looked at:

1. Alternative, lower emission propulsion technologies, ranging from electric aircraft with batteries as energy source, different propulsion hybrids, and new concepts for Jet-fuel and Hydrogen gas turbine engines.
2. We have also reviewed recent research on the role of CO2, NOx emissions, and Contrails generated by airliners in global warming.
3. Two weeks ago, we summarized the present situation around SAF, Sustainable Aviation Fuel.

Last week, we listed some base data about the present situation for Global Air Transport. We will now use this data to calculate the effect of air transport on global warming from the three alternatives.

Emission-free airliners

Let’s start by imagining a scenario in which we are successful in producing CO2 and NOx emission-free airliners based on the different projects we examined. These projects can replace the existing 19, 30 to 50-seat, and 70 to 100-seat turboprops in the market.

We assume 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.

Aircraft production ramp is more challenging than most alternative propulsion projects realize. Here, we assume a best-case scenario where production in the first year is one aircraft per month. Then, this is doubled for year two, with a 50% increase in yearly production rate thereafter until a maximum production of 100 aircraft per year is reached.

This level is not the maximum these companies can ramp to; it’s what the market accepts in terms of new aircraft sales to replace older turboprops in these market segments. The resulting yearly output of emission-free airliners is shown in Figure 2.

Figure 2. The yearly replacement of CO2 and NOx-emitting Turboprops. Source: Leeham Co.

From the table, we can see we replace a total of 1800 older 19 seaters and 1800 30 to 50 seaters. Finally, 800 70 to 100 seaters get replaced. These aircraft consume per year:

• 19 seaters around 1,000 tonnes Jet-A1 per year. In the year 2050, we have replaced 1,800 Turboprops in total. During 2050, these emission-free 19-seaters would save 1.8 million tonnes of Jet fuel from being consumed.
• 30 to 50 seaters, around 1,900 tonnes Jet-A1 per year. In the year 2050, we will have replaced 1,800 Turboprops in total. During 2050, these would save 3.4 million tonnes of Jet fuel from being consumed.
• 70 to 100 seaters, around 2,500 tonnes Jet-A1 per year. In the year 2050, we have replaced 800 Turboprops in total. During 2050, these would save 2 million tonnes of Jet fuel from being consumed.

In total, by 2050, the Jet-A1 consumption in these airliner segments would have reduced by 7.2 million tonnes.

Last week, we learned that the yearly consumption of Jet-A1 for Air Transport is around 300 million tonnes. If the market introduces more efficient jet aircraft up until 2050, which keeps consumption at about the same level, we will save 2.4% of Jet-A1 from being burned in gas turbines.

As there is a direct relation between CO2 emissions and Jet fuel consumption, the savings in CO2 emissions would also be 2.4%.

Over the next Corners, we will compare these savings to the other Global Warming mitigating measures we listed above.