Leeham News and Analysis
There's more to real news than a news release.
What’s the status of the alternative propulsion projects for air transport?
Subscription required
By Bjorn Fehrm
November 13, 2025, © Leeham News: The interest for new and more environmentally friendly aircraft got underway in 2014, when Airbus flew the battery-electric E-fan demonstrator at the Farnborough Air Show in July, Figure 1.
The car revolution to battery-electric cars had taken off two years earlier, when Tesla introduced the Model S sedan with elegant styling and very good performance and economy for a family car (Figure 1).
Figure 1. The battery-electric aircraft demonstrator and the car that started it all. Credit: Airbus and Tesla Inc.
Tesla cars had proven that electric cars could match and even outpace combustion-engine cars in performance and operational costs, though not in driving range. But range was a matter of battery capacity development, and hopes were high for a similar situation and development for aircraft.
As is the case with almost every technological leap, the progression of alternative propulsion aircraft projects followed the Gartner Technology Hype curve (Figure 2).
Figure 2. The Gartner Hype Curve for alternative propulsion aircraft. Credit: Gartner and Leeham Co.
The start was around 2015, passing the Peak of Inflated Expectations around 2020. In the 11 years since 2014, we’ve had hundreds of entrepreneur-driven projects declare they will make environmentally friendly aircraft and airliners a reality.
Nothing useful has come out of these projects, so today, we are passing the Trough of Disillusionment. Investors have stopped funding alternative propulsion startups as these have not produced useful air transport. The result is a mass death of projects, most silently, some more openly.
The core of the remaining projects are run by experienced teams with solid aeronautical knowledge. These are now passing into the Slope of Enlightenment and will make real progress. Given that we are now entering a more productive phase, we take stock of these developments and their programs.
To help the analysis, we use our Aircraft Performance and Cost Model, APCM, to show what the challenges are and how alternative propulsion can address these challenges.
What’s the next new aircraft, Part 5
By Scott Hamilton and Bjorn Fehrm
July 31, 2025, © Leeham News: We wrap up our five-part series today on What’s the Next New Airplane in the coming decades. We now look at Airplanes 9-13 in Figure 1 below.
Figure 1. The 13 airliners we look at in the series. Source: Leeham Co.
These are the (9) COMAC 929, (10) Eco-version of New Light Twin, (11) CFM Open Fan single aisle, (12) the Boeing 787 re-engine, and (13) the Airbus A350 re-engine.
Bjorn’s Corner: Air Transport’s route to 2050. Part 32. Epilogue.
By Bjorn Fehrm
July 25, 2025, ©. Leeham News: In October last year, we began a series on how air transport is performing against the emission goals for the year 2050.
The ambition to reduce and eventually eliminate greenhouse gas emissions began in earnest 11 years ago, when Airbus flew the Airbus E-Fan at the 2014 Farnborough Air Show (Figure 1).
Figure 1. The Airbus E-fan flying at the 2014 Farnborough Air Show. Source: Wikipedia.
The result of this inspiring flight, which utilized technology that emitted no CO2 or other greenhouse gases (if the batteries were charged with green electricity), was an avalanche of projects from established players as well as upstarts. The optimistic view was that there was a solution to the emissions from airliners.
Bjorn’s Corner: Air Transport’s route to 2050. Part 28.
By Bjorn Fehrm
June 27, 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 explored various methods to mitigate global warming throughout the series. Over the last few weeks, we have summarized the practical results we can expect from the different alternatives available to reduce global warming in air transport. We looked at the following:
- Alternative, lower-emission propulsion technologies.
- The industry’s typical improvement in fuel consumption over time.
- The improvements that SAF can offer by 2050.
- The different Emission Trading Schemes (ETS) that exist globally.
- And finally, what warming contrail reductions can achieve.
We have summarized what the first four actions can achieve by 2050 and presented the results in a table, Figure 1. Now we add what global warming contrail avoidance can do.
Figure 1. The effects of Actions 1 to 4 on CO2 and NOx counted as CO2e emissions by 2050. Source: Leeham Co.
Electric Flight and the Ugly Duckling
By Bjorn Fehrm
June 25, 2025, © Leeham News at Paris Air Show: The low or no emission propulsion discussion started at the 2014 Farnborough Air Show when Airbus’ E-Fan prototype flew in front of a surprised crowd. Everyone then thought that low-emission electric propulsion aircraft would be common before 2020.
It took 11 years and as many air shows before a certifiable battery-electric aircraft would fly again at an air show, this time at the 2025 Paris Air Show (Figure 1). Of the over 100 announced projects to develop and produce a battery electric passenger aircraft, it was the Alia CX300 from BETA Technologies that succeeded.
The story of BETA Technologies’ Alia CX300 is, in many ways, the story of the Ugly Duckling that grew to become a White Swan.
Figure 1. The BETA Alia CX300 battery-electric cargo version ready for its daily Paris Air Show flight. Source: Paris Air Show.
Bjorn’s Corner: Air Transport’s route to 2050. Part 27.
By Bjorn Fehrm
June 20, 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:
- Alternative, lower-emission propulsion technologies.
- The industry’s typical improvement in fuel consumption over time.
- The improvements that SAF can offer by 2050.
- The different Emission Trading Schemes (ETS) that exist globally.
- Finally, what warming contrail reductions can achieve.
Bjorn’s Corner: Air Transport’s route to 2050. Part 26.
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:
Bjorn’s Corner: Air Transport’s route to 2050. Part 25.
By Bjorn Fehrm
June 6, 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 examined alternative, lower-emission propulsion technologies four weeks ago and compared them the following week to the industry’s typical improvement in fuel consumption over time. Then, we examined the improvements that SAF can offer by 2050. Last week, we complemented the picture with the different Emission Trading Schemes (ETS) that exist globally.
Now, we discuss what warming contrail avoidance could achieve in reducing global warming.
Figure 1. A summary of the CO2 and non-CO2 Effective Radiative Forcing (ERF = warming effect) 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 23.
By Bjorn Fehrm
May 23, 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 looked at recent research into the role of CO2, NOx emissions and Contrails generated by airliners.
- Three weeks ago, we summarized the present situation around SAF, Sustainable Aviation Fuel.
We examined Alternative 1’s emissions improvement two weeks ago and compared it to the normal improvement in new airliners’ fuel consumption last week. Now, we examine the improvement that SAF can offer compared to the other two.
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:
-
- 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.