Credit: Hybrid Air Vehicles Ltd
by Graham Parkhurst, Professor of Sustainable Mobility and Director of CTS
January 2025 saw the latest chapter opened in the decades-long Heathrow additional runway saga, and by none other than the Chancellor of the Exchequer. Rachel Reeves argued that ‘greener’ aviation could make crossing this hitherto environmental Rubicon thinkable.
The reality, though, is that a low environmental impact version of the business model currently delivered by airliners equipped with turbofans burning kerosene remains a theoretical possibility subject to an uncertain delivery date. Say it took a decade to deliver the new runway, it would open in 2035. That is the year that Airbus has the “ambition” to deliver its first hydrogen-powered commercial aircraft. The keywords in that sentence are ‘ambition’ and ‘first’. Also in 2035, according to a UK Government mandate , 15% of aviation turbine fuel supplied in the UK must be Sustainable Aviation Fuel (SAF). But that suggests 85% (of a growing volume) won’t be. SAF is also a controversial option. It is not in fact ‘jet zero’. According to the International Air Transport Association, SAF can reduce carbon dioxide emissions by up to 80%. And there are major concerns that production at the scale necessary for this to be a significant solution could only be achieved by using scarce agricultural land.
By 2035, assuming these modest ambitions are realised, and replicated around the globe, we would have 15 years left to avoid or offset the vast majority of greenhouse gas emissions from aviation and would only just be beginning to replace jet aircraft fleets with hydrogen-powered alternatives. In the absence of a viable strategy to reduce emissions faster, the current aviation business model seems to be broken in terms of climate heating. But aviation has some advantages within the transport system, such as being able to seamlessly cross land and sea and needing terminal infrastructure only in specific places. It is important then to consider whether there are more radical alternative technologies and business models which can offer much lower greenhouse gas emissions in the near future. One such potential lies with Hybrid Air Vehicles’ ‘Airlander‘.
Lighter-than-air craft are not new. For a few years in the 1930s airships such as the Zeppelins seemed to represent the future for passenger aviation. Graf Zeppelin circumnavigated the globe in 1929 and made 64 round trips between Germany and Brazil, establishing the first regular intercontinental commercial air passenger service.
Zeppelin passenger services ended with the infamous demise of the Hindenberg at New Jersey in 1937, but Airlander represents a radically different approach. Being a hybrid aircraft, a helium-filled envelope gives 60% of its lift, like a balloon. Helium is an inert, non-inflammable, so safe, gas. The other 40% comes from aerodynamic lift, like a fixed-wing aircraft. The first series, Airlander 10, will be able to carry over 100 passengers or 10 tonnes of freight, or a combination of the two. Even if kerosene is used for propulsion, the energy consumption and carbon emissions are up to 75% lower than a comparable conventional fixed-wing aircraft. But it is intended that, by 2030, Airlander will produce zero greenhouse gas emissions from flight by using hydrogen fuel cells to power electric motors. Unlike fixed-wing jet aircraft, Airlander is well-suited by design to accommodate onboard hydrogen storage.
Another advantage of Hybrid Air Vehicles’ (HAV) approach is that Airlander flies at a lower altitude, so contrail production can be avoided. Contrails contribute to the radiative forcing that causes climate change. Flying lower also means cabin pressurisation is not necessary, which is better for passenger health.
Airlander requires minimal ground infrastructure, so a broad range of destinations can be served directly, minimising investment needs and the environmental impacts of traditional airport infrastructure.
So, if hybrid aircraft can offer safe, green, accessible and healthy air services, ‘what’s the catch?’ you might be asking. A key difference with most current aviation business models is speed. Airlander’s cruising speed is around 70 knots (130kmh / 80 mph), up to eight times slower than an airliner. Whether this is a ‘catch’ or not depends on the niche we expect a hybrid aircraft to serve, and the emphasis that different users place on minimising travel time.
A transatlantic trip might take up to two days rather than 7-8 hours. If the journey is seen as something to overcome and endure then two days will be seen as a problem. Alternatively, the trip might be seen as an air cruise, valuable in itself, with passengers able to enjoy the view through large windows, made possible by the unpressurised cabin, whilst seated or lying comfortably, as space is at less of a premium than onboard a jet.
Credit: Hybrid Air Vehicles Ltd
Many flights, though, are much shorter than crossing the Atlantic. As flight distance falls, the share of time spent airborne relative to the overall journey time also falls. Time due to surface journey legs and passing through terminals becomes relatively important. Airlander will minimise the use of access modes by serving locations directly, made possible by being ‘infrastructure light’. Early applications are expected to connect islands.
Other niches could arise with applications currently served by surface transport modes. In 2023 the then UK Government decided not to proceed with high-speed rail north of London-Birmingham. An affordable alternative might be to serve communities which will not now receive faster rail services with a network of Airlander routes from an interchange near the new Birmingham Curzon Street station.
As with all new technologies and services, though, customers will need to trust hybrid aircraft and perceive them to be useful and useable. In 2023-2024 Chris Parker, Chen Liao, and I collaborated in a research project called Co-Creation of Future Flight Ecosystems and Enterprise (CoFFEE). One element of the project involved a survey of people living in the Doncaster area, where Airlander aircraft are to be built. The analysis covered awareness of Airlander, views on hosting the production facility, and perceptions of Airlander as a future transport option.
Credit: Hybrid Air Vehicles Ltd
Most of the 277 respondents had at least heard of Airlander and distinguished it as something different from current passenger jets. The overwhelming mood of respondents was that hosting the Airlander production facility would be good for the local area, even if there were some concerns about the impacts of constructing and operating the factory.
Concerning Airlander as a means of transport, the perceived relevance of Airlander was highest for air services that would not in fact move people (freight, aerial surveying), but passenger travel between UK towns as well as leisure trips such as air cruises were also identified as options by many. Travel for holidays abroad was though selected by fewer than a quarter of respondents.
Which of the following can you imagine Airlander might be used for?
Consistent with these responses, given the operational speed of Airlander, was the willingness of participants to spend more time travelling if it would be better for the environment. Three-fifths of participants indicated that they would be prepared for a one-hour flight to instead take twice as long and approaching a third would accept three hours or longer. Just a tenth was prepared to spend only slightly longer, or no longer at all.
We said above that Airlander is better for the environment than a jet aircraft. Imagine you are thinking about making a journey that takes one hour on a jet plane. How much longer would you be willing to spend travelling to help the environment?
These views are based on a hypothetical trip and considering only the journey time and environmental impact as explicit factors. Respondents would not have experienced travel on an Airlander. The overall positive associations about hosting the production facility may have influenced responses about Airlander as a form of mobility. Nonetheless, the results suggest strong personal concerns about the environmental impacts of aviation and willingness, at least in principle, to make compromises to be able to fly with lower impacts, at least for short-haul flights.
Future research should explore how these trade-offs might be made in practice. In the same way that train travel is promoted as an alternative to flying by jet, Airlander could offer a moderate-speed alternative, for those not well served by rail services. The business model could include a generous onboard space allocation per passenger and sleeper services, so the travel time is used ‘productively’. Avoiding some of the constraints of rail travel, by offering a wide range of direct services and avoiding reliance on track infrastructure would retain some key aviation advantages.
This blog was written by Prof Graham Parkhurst, Professor of Sustainable Mobility and Director of CTS, University of the West of England, Bristol.
Graham was co-investigator in the project Co-Creation of Future Flight Ecosystems and Enterprise (CoFFEE) led by Dr Chris Parker (Loughborough University) between May 2023 and November 2024 and funded by UKRI as part of the Future Flight Social Science initiative coordinated by the University of Birmingham. For any questions or comments about this blog please email graham.parkhurst@uwe.ac.uk.