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What’s the status of the alternative propulsion projects for air transport?
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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.
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 29.
By Bjorn Fehrm
July 4, 2025, ©. Leeham News: We feature a Corner series on the state of actions to mitigate the global warming impact from Air Transport. We try to understand why different developments have been slow.
In the last Corner, we wanted to understand the relationship between Greenhouse gas emissions of CO2 and NOx and the effect of global warming from contrails. After some iterations, we arrived at the comparison shown in Figure 1, where we compare different warming effects using CO2 and CO2e (CO2 equivalents, i.e. the same warming effect as CO2).
Figure 1. The Global waring effect of CO2, NOx and warming contrails by 2050 as CO2 and CO2e. Source: Leeham Co. Click to enlarge.
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 9.
By Bjorn Fehrm
February 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 the development has been slow.
We have covered the progress of battery-based aircraft and hybrids. Last Corner started looking at hydrogen-fueled alternatives. A day after the Corner, the Airbus workers union Force Ovrier published information from an Airbus internal meeting, in which the airframer delayed the introduction of a hydrogen aircraft by 2035 to about 10 years later. As a consequence, it reduces the R&D spending on the development of hydrogen propulsion technologies.
Figure 1. The Airbus ZEROe concepts. Source: Airbus.
Bjorn’s Corner: Air Transport’s route to 2050. Part 8
By Bjorn Fehrm
February 7, 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 the development has been slow.
We have covered the progress of battery-based aircraft and hybrids, where the last Corner was about the most sensible hybrids, the mild hybrids. Now, we turn to hydrogen-fueled alternatives.
Figure 1. The operation of a PEM fuel cell. Source: NASA.
Bjorn’s Corner: Air Transport’s route to 2050. Part 7.
By Bjorn Fehrm
January 31, 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 the development has been slow.
We have covered the progress of battery-based aircraft and hybrids, both serial and parallel hybrids. A couple of mild hybrids have a larger chance of success than the ones we described. We will look into these and then start looking at different hydrogen-fueled alternatives.
Figure 1. The LEAP-1A with auxiliary gearbox. Source: Safran Transmissions.
Bjorn’s Corner: Air Transport’s route to 2050. Part 6.
Bjorn Fehrm
January 24, 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 the development has been slow.
We have covered why the progress of battery-based aircraft is slow and also described what to expect at the end of this decade and the beginning of next.
Now, we look at hybrids, an inherently more complex design. Upstarts are changing to hybrids after realizing that battery-only aircraft will not have useful range this side of 2030.
Figure 1. The Heart Aerospace ES-30 has passed the phases in the article. Source: Heart Aerospace.
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Bjorn’s Corner: Air Transport’s route to 2050. Part 5.
By Bjorn Fehrm
January 17, 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 the development has been slow.
We have covered why the technical progress of battery-based aircraft has been slow. Now we look at what type of missions it can do this decade and beyond and why the limitations.
Figure 1. The Diamond eDA40 electric trainer. Source: Diamond. Read more
Bjorn’s Corner: Air Transport’s route to 2050. Part 4.
By Bjorn Fehrm
January 10, 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 the development has been slow.
We listed the different projects in the second Corner of the series that have come as far as flying a functional model or prototype. In Part 3, we went through some of the causes of the slow growth. It was a mix of inexperienced startup managments, all wanting to be the new Elon Musk but lacking elementary knowledge in the aeronautical field, to what is the real hard part of an alternative propulsion concept.
Many startups developed new electric motors for eAirplane or eVTOL use, a relatively straightforward development when the real hard part is the batteries. We described how batteries differ significantly from fuel as an energy source in Part 3.
Now, we add a market aspect that is poorly understood by most players.
Figure 1. The Pipistrel Velis Electro trainer. Source: Pipistrel.