Leeham News and Analysis
There's more to real news than a news release.
Leeham News and Analysis
- Services are driving revenues and profits in difficult times, Part II May 22, 2025
- Boeing publicizes fourth Chief Aerospace Safety Officer Report May 21, 2025
- Boeing’s 2025 annual safety report due this month May 20, 2025
- FAA’s data of accident, incidents, often not shared May 19, 2025
- Bjorn’s Corner: Air Transport’s route to 2050. Part 22. May 16, 2025
Bjorn’s Corner: Air Transport’s route to 2050. Part 22.
By Bjorn Fehrm
May 16, 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 since we started in October last year looked at:
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- 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.
- We have also reviewed recent research on the role of CO2, NOx emissions, and Contrails generated by airliners.
- Two weeks ago, we summarized the present situation around SAF, Sustainable Aviation Fuel.
We examined Alternative 1’s emissions improvement last week and now compare it to the normal improvement in fuel consumption, and thus emissions, that the airline industry is continuously working on.
Bjorn’s Corner: Air Transport’s route to 2050. Part 21.
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:
- 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.
- We have also reviewed recent research on the role of CO2, NOx emissions, and Contrails generated by airliners in global warming.
- 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.
Bjorn’s Corner: Air Transport’s route to 2050. Part 20.
By Bjorn Fehrm
May 2, 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 since we started in October last year looked at:
- 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.
- We have also reviewed recent research on the role of CO2, NOx emissions, and Contrails generated by airliners.
- Last week, we summarized the present situation around SAF, Sustainable Aviation Fuel.
Before we proceed, we shall examine some facts about the scale of the emission/global warming influences from Air Transport.
Figure 1. A picture of global Air Transport flying different routes. Source: Flightradar24.
Bjorn’s Corner: Air Transport’s route to 2050. Part 19.
By Bjorn Fehrm.
April 25, 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.
Over the last Corners, we examined the non-CO2 effects of Air Transport that contribute to global warming. Contrails had the largest effects, even larger than the CO2 emissions from Air Transport.
To complete the review of our progress with lower emission actions for Air Transport, we will examine the present situation with SAF, Sustainable Aviation Fuel.
Figure 1 The main production pathways to SAF. Source: Clean Skies for Tomorrow report. Click to enlarge.
Bjorn’s Corner: Air Transport’s route to 2050. Part 18.
By Bjorn Fehrm
April 18, 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 examine the non-CO2 effects of Air Transport that contribute to global warming. Over the last weeks, we have looked at contrails, which have the largest impact on global warming, larger than CO2, Figure 1.
NOx is a smaller contributor, but it contributes about 20% of the total to Global Warming.
Figure 1. A summary of the CO2 and non-CO2 Effective Radiative Forcing (ERF) contributions from Air Transport. Source: The report “The contribution of global aviation to anthropogenic climate forcing for 2000-2018” by Lee et al. (2021).
Bjorn’s Corner: Air Transport’s route to 2050. Part 17.
By Bjorn Fehrm
April 11, 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 now examine the non-CO2 effects of Air Transport that contribute to global warming. Of these, contrails have the largest impact, Figure 1.
In the last Corner, we described encouraging results from airline flight trials with warming contrail avoidance. What is required to move from trials to warming contrail avoidance for regular flights?
Figure 1. A summary of the CO2 and non-CO2 Effective Radiative Forcing (ERF) contributions from Air Transport. Source: The report “The contribution of global aviation to anthropogenic climate forcing for 2000-2018” by Lee et al. (2021).
Bjorn’s Corner: Air Transport’s route to 2050. Part 16.
By Bjorn Fehrm
April 4, 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 now examine the non-CO2 effects of Air Transport that contribute to global warming. Of these, contrails have the largest impact.
Contrails form when aircraft gas turbine engines emit soot particles into water vapor-saturated areas with low temperatures, where the soot particles act as condensation nuclei and the droplets freeze into ice crystals.
The report from Lee et al. (2021) lists non-CO2 effects as more important for Global Warming from Air Transport than CO2 emissions from burning hydrocarbon fuels, Figure 1.
Figure 1. A summary of the CO2 and non-CO2 Effective Radiative Forcing (ERF) contributions from Air Transport. Source: The report “The contribution of global aviation to anthropogenic climate forcing for 2000-2018” by Lee et al. (2021).
Bjorn’s Corner: Air Transport’s route to 2050. Part 15.
March 21, 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.
After covering alternative propulsion concepts to lower CO2 and NOx emissions, we now study air transport’s non-CO2 effects on global warming. Of these, contrails have the largest impact.
Contrails form when aircraft gas turbine engines emit soot particles into low-temperature water vapor-saturated areas in the atmosphere. The soot particles form condensation nuclei, and the developed droplets freeze to ice crystals that form contrails.
Figure 1. The net Radiative Forcing of flights during 2019. Source: The report “Global aviation contrail climate effects from 2019 to 2021” from 2024.
Bjorn’s Corner: Air Transport’s route to 2050. Part 14.
By Bjorn Fehrm
March 21, 2025, ©. Leeham News: We do a Corner series about the state of developments to replace or improve hydrocarbon propulsion concepts for Air Transport. We try to understand why development has been slow.
Last week, we examined MTU’s WET engine concept, which utilizes a water capture process in a Turbofan to lower emissions, such as NOx, and reduce the water content in the exhaust, thereby reducing contrail risk. The week before, we looked at a similar concept, focused on a hydrogen burn process from Pratt & Whitney called HySIITE.
Both concepts capture water in the turbofan’s exhaust and can then release it in a way that avoids contrail generation. Contrails have garnered significant attention in recent years, as research has raised the possibility that persistent contrails can contribute as much or more to global warming than the CO2 released during the Turbofan combustion process in an airliner.
We will spend the next Corners digging deeper into the question of air transport’s non-CO2 effects that contribute to global warming. Contrails have the largest impact on these non-CO2 contributions.
Figure 1. The complex interaction of different heat radiation and blocking processes in our atmosphere. Source: The report “The contribution of global aviation to anthropogenic climate forcing for 2000-2018” by Lee et al.
Bjorn’s Corner: Air Transport’s route to 2050. Part 13.
By Bjorn Fehrm.
March 14, 2025, ©. Leeham News: We do a Corner series about the state of developments to replace or improve hydrocarbon propulsion concepts for Air Transport. We try to understand why development has been slow.
Last week, we summarized the well-to-use efficiency gain of the Pratt & Whitney HySIITE engine process, which was announced in January. We found that with an expected 35% increase in engine efficiency, the liquid hydrogen chain, from the splitting of water into hydrogen and oxygen through liquefaction to burning it in the engine, used less renewable energy than if we used the same method to make Power to Liquid (PtL) SAF.
Pratt & Whitney was very clear in the presentation that the evolution of a HySIITE engine is a long-term project, with its possible use on the other side of 2040. There are just too many new components (heat exchangers, evaporators, etc.) that need development and maturation to think this is a near-term engine opportunity.
MTU’s similar WET engine concept, Figure 1, uses the same process ideas but with a different target. Here, the focus has been reducing emissions, like NOx and water content in the exhaust, to reduce contrail risk. This shall be achieved when burning jet fuel, SAF, and hydrogen.
Figure 1. An MTU WET engine with its straight core. Source: MTU.