If most airlines stop buying conventional large airliners and order big hydrogen airliners instead, the amount of CO2 produced by aviation in the period 2030 to 2050 could be much less than currently forecast, and less than taking any other approach.

The main reason the airlines will respond enthusiastically to this plan is because liquid hydrogen is expected to cost much less than FAS or kerosene by 2035, and will continue to fall in price. This will make the business case simple, with the added bonus of an increase in traffic due to the removal of ‘flight shame’.

The new airliners can be developed swiftly and relatively cheaply because they can be based closely on two existing offerings, the Airbus A350-1000 and the Boeing 777-8. It is even possible that the actual aircraft Airbus will modify to form the first prototype has already flown. If so, it will be almost identical in appearance to the A350F freighter version pictured.

Since multiple hydrogen tanks small enough to pass through the freighter version’s large cargo-loading door can provide enough fuel for test flights, there will be no need to wait for the development of the very large integrated rear tank required in the production freighters and the hydrogen airliners.

This should help make the end of 2025 credible as the target for the first flight of the A350FH prototype, with one of its Rolls-Royce Trent engines running on hydrogen and the other fuelled conventionally.

Then the first 350-seat A350H prototype, based on an A350-1000, could be flying by the end of 2027, powered by two Rolls-Royce UltraFan engines, both running on hydrogen, and optimally-sized for the A350H and FH. Warren East, the retiring CEO of Rolls-Royce, was recently quoted as saying:- “We can’t wait for hydrogen!”

His successor, Tufan Erginbilgic, will now need to ensure Airbus doesn’t have to wait for Rolls-Royce, or GE will be delighted to provide an alternative!

France will lead, helped by the EU’s new tax on aviation fuel
In October 2021 President Macron gave a speech entitled “France 2030” in which he outlined the ten key objectives of his next term, if re-elected. The second objective on his list was for France to become the leader in green hydrogen.

The fifth was to produce the first low-carbon aircraft by 2030. In his speech he mentioned that the experts he had consulted had told him that this would not be possible before 2035, but he still believed that 2030 was a reasonable target. And it now turns out that he was right, mainly because of the impact on the world’s energy systems of Russia’s invasion of Ukraine.

The ‘global elite’ will rejoice
Recent research by the Norwegian Centre for Energy Transition Strategies shows that a global elite of just 1% of the world’s population generates roughly half of all the global carbon emissions from aviation. Until recently, the experts had told them that it would take until 2035, at the earliest, for the price of hydrogen to have fallen to a level where it would make financial sense for the airlines to use it operationally, not just to fuel a few small airliners as a PR exercise.

Consequently, there seemed no need for the rapid development of ‘proper’ hydrogen airliners. This still appears to be the position of both Boeing and Airbus, with Airbus intending to have a single-aisle offering with a range of 2,000 nautical miles ready by 2035, probably based on the A320neo.

However, once the global elite becomes aware that the massive investments they are making in green hydrogen will result in it becoming the obvious way to fuel aircraft they will apply pressure on Airbus and Boeing to produce airliners that can use it as soon as practical.

Despite being a strong supporter of actions to combat Climate Change, Bill Gates apparently flew the equivalent of four times around the world in 2017, presumably because he felt the effort was necessary, despite the inevitable accusations of hypocrisy. Now imagine how strongly he wants this problem solved, and what he may be prepared to do to make it happen, once he becomes aware there is a credible near-term answer.

Using large hydrogen airliners as early as practical will really help the climate
From a climate perspective, the sooner airliners are fuelled by hydrogen the better, as the simple diagram below illustrates. Starting operational flights in 2030 would save some 78% more CO2 by 2050, compared with waiting for take-off until 2035. And the benefits would continue well beyond 2050.

Some of the leading European airlines may already be asking Airbus and Boeing to develop large hydrogen airliners which will be able to enter service by 2030. The main reason is that it will already cost less to use hydrogen in Europe than heavily-taxed kerosene by 2030, and much less by 2040, when an airliner bought in 2030 will be less than halfway through an average 26-year operating life.

So a key question each airline may already be asking itself is – ‘when should we begin to reduce our orders for new conventional airliners, and wait for their hydrogen-powered replacements?’ The motivation, as usual, will be to keep down the cost of flying; the resulting green image will be just a bonus. This presents Airbus and Boeing with the spectre of a big fall in demand until they can supply what their customers really want – clean airliners that are cheap to fly. The impact of starting early – over 75% more CO2 saved 2030 2035 2040 2045 2050

The airlines will decide
The usual reason why airlines decide to start ordering a new type of airliner is because it delivers a lower cost per passenger-km than their current aircraft. This is now why they will want to bring hydrogen-powered airliners into service as soon as possible.

The main reason for this new urgency is the increase in the price of conventional fuels caused by the invasion of Ukraine, and its impact on plans to develop wind, solar and nuclear power, which is now expected to result in an abundance of low-cost green hydrogen globally by 2035. The invasion has already provoked massively increased investments in renewables and hydrogen.

On February 1 this year, the European Commission unveiled its Green Deal Industrial plan with the intention of offering green hydrogen producers a subsidy programme; its REPowerEU plan is already leading the way, quadrupling the EU’s existing green hydrogen consumption target for 2030 to 20.6m tonnes per year. And in June 2021, well before the invasion, the US Department of Energy set a hydrogen cost target of $1/kg by 2031, which now looks increasingly realistic and prescient.

Trucks will be way ahead of airliners
Aware of all this, Daimler, Volvo and others are developing large long-haul fuel-cell trucks running on liquid hydrogen, and selected customers are expected to begin testing them in two years’ time.

Green hydrogen is now predicted to become not just cost-competitive but also widely available across Europe because the EU Parliament has already passed legislation that will require the hydrogen filling stations on main routes to be less than 150km apart, resulting in an estimated thousand filling stations being in place by 2030. And a proposal is being debated to reduce the maximum distance between filling stations to 100km, and achieve this by 2027.

If passed, this should result in some 1,500 hydrogen filling stations across Europe in only five years’ time. So by 2030 several large hydrogen delivery trucks should be able to carry enough liquid hydrogen to refuel a big hydrogen airliner at almost any airport in Europe before the first hydrogen airliners are
in service, even if the aggressive amendment is not approved.

However, it is now expected that hydrogen gas pipelines will have been connected to most major European airports by 2035, with liquefaction on site. So the truck delivery solution is likely to become confined to small or remote airfields. But the key point is that the global haulage industry will initially use far more green hydrogen than aviation, and the evidence should be obvious on European roads well before most airlines place orders for their first large zero-carbon airliners.

Traffic forecast
The DLR’s long-term forecast is likely to remain the basis for predicting the size and number of new airliners needed in each sector of aviation because the DLR (aka the German Aerospace Centre) is the EU-funded Clean Aviation Joint Undertaking’s primary source of traffic forecasts, amongst its many other roles. The key chart is below:

Shown below is the same chart with the scope of Airbus’s ZEROe project (up to 200-seats and a maximum range of 2,000 nautical miles) and the ‘H350’ solution (350 seats, 6,000km) added to it:

The CO2 column shows the percentage share of the total amount of CO2 that would be produced by aviation if kerosene was still the only fuel used. So the DLR sees planes with less than 210 seats as less than 13% of the CO2 emission problem! And the CO2 row shows flights of over 6,000km contributing 23%, so hydrogen-fuelled A350s and 777s, alone, will be capable of addressing almost 70% of aviation’s target.

The DLR’s key conclusion was that “the main focus on decarbonising aviation should be on short-range aircraft flying distances of less than 4,000 km, however with much larger passenger capacity, well over 300, even over 400 passengers in the cabin.” It seems Airbus is still aiming its development efforts at today’s narrow-body body market, not at producing the big widebody hydrogen-powered airliners which are already predicted be in strong demand by the time they can be available.

Follow the money
There is general agreement that biofuels can only provide a small percentage of the total amount of SAF needed to replace conventional jet fuel. The currently popular alternative is PtL (Power-to-Liquid), produced by using electricity from renewables to electrolyse water and to extract CO2 from the atmosphere, and then use more energy to combine them to produce a liquid which emulates kerosene.

Clearly, the PtL process will need more energy than required to produce liquid hydrogen, and the production equipment required will cost more. But Boeing seems to think SAF is the best answer because it’s easy. Here’s a quote from an interview in October last year with Marc Allen, Boeing’s Chief Strategy Officer. “We have shifted our language from zero emissions to zero impact. Hydrogen might have a role, but that might be being used on the ground to produce SAF…” Not surprisingly, the Aerospace Technology Institute seemed at odds with Boeing’s position.

Now imagine it’s 2033, and the cost of hydrogen has met the US Department of Transport’s $1/kg target. An Air France A350H is being fuelled for a flight from Paris to NEOM, Saudi Arabia, a distance of almost 4,000km. A conventional A350 would consume approximately 35 tons of Jet A-1 or PtL, but an A350H will probably need less than 12 tons of liquid hydrogen. Jet A-1 currently has a price of slightly less than $1/kg because it’s almost free of tax, but the EU is planning to introduce an aviation fuel tax from 2023 which is now expected to raise the price to at least $2/kg H350 ZEROe by 2033.

If the price of liquid hydrogen is slightly less than $2/kg by the time it’s in the aircraft (and only $1.5/kg in NEOM?), it will cost under $30,000 to fuel the A350H. However, it will probably cost around $75,000 by 2033 to provide a conventional A350 with enough Jet A-1 for the outbound flight, although the return would be a lot cheaper. This suggests an outbound ticket on a conventional A350 or 777 may need to be around $150 more expensive to cover the extra cost of Jet A-1.

What about SAF? Current estimates are that PtL is likely to cost at least twice as much per km as hydrogen by 2035, and require much more renewable electricity to produce it. So how soon before the current enthusiasm for SAF fades away? Perhaps among the leading airlines first?

A recent study by the EU’s Clean Sky joint undertaking and McKinsey predicted that hydrogen will be radically cheaper than jet fuel by 2050. The price of synthetic fuel is around $450 per MWh at present, though this is expected to decrease to less than $250 by 2050. However, liquid hydrogen is predicted to reduce even more, perhaps to as low as $50 – in Saudi Arabia?

This now suggests the market window for SAF will begin to close before 2035 because by then it will cost most airlines considerably less to operate hydrogen-powered airliners than those running on SAF or Jet A-1. Consequently, the leading low-cost airlines and lessors will probably be keen to order A350Hs and/or 777-Hs well before they become available in any quantity.

A key date for every airline will be when it believes it will cost less per PKM (passenger-kilometre) to use hydrogen rather than kerosene for its particular traffic characteristics, even allowing for the loss of five(?) rear rows of passenger seats. Each airline will then calculate when it should begin to minimise its orders for conventionally fuelled aircraft and wait for the first hydrogen-powered airliner which meets its particular size and range requirements.

This is likely to be several years before there is an annual cost advantage because its calculations will be based on the fuel prices over the life of the aircraft, so it will make sense to begin to operate hydrogen airliners well before there is fuel price parity, because of the marketing benefits.

The European Commission has ensured that this will be earlier in Europe than in the rest of the world by gradually introducing a tax on conventional aviation fuel which may have reached rough parity with the tax on petrol by 2031.

The DLR has produced a global forecast which suggests that, by 2050, most air passengers will be carried in airliners with some 400 seats over flights of less than 4,000 km. Because it will make most commercial sense to start using hydrogen airliners for flights within Europe, the DLR’s 2050 forecast should now prove correct for Europe by 2040, if not earlier.

The relatively short maximum range required will make it possible to base the new aircraft on an existing large airliner, such as the Airbus A350 or the Boeing 777, and develop hydrogen versions quickly and relatively cheaply. The first prototype A350H, based on an A350-1000, could be in the air by 2026, and A350FHs might be operated by the military from 2028 onwards. All being well, the first passenger flights could be as early as 2030.

By Air France and easyJet? The new airliners should also prove ideal in the large Chinese and Indian internal markets by 2035, when the price of liquid hydrogen is already forecast to have fallen even further, to less than untaxed kerosene and much less than any SAF.  The systems engineering study showed that the maximum range possible for the A350H concept outlined here could be as much 6,000km (using additional hydrogen storage space in the lower
fuselage between the wings), which will be enough to meet the UK government’s Jet Zero transatlantic flight requirement.

Conclusions
1. By the end of this year, if not earlier, President Macron will have encouraged Airbus to upgrade its ZEROe project, and base it initially on the A350F, the freighter version of the A350. And he may have ordered the first A350FH for the French Air Force. He will probably also have reminded Air France that it agreed to work towards becoming “the world’s most environmentally friendly airline” as a condition of the lavish funding it received during the Covid epidemic. Consequently, Air France may be encouraged to place a conditional order for a large number of A350Hs well before any other airline.

2. Because the prototype will be based on an A350F it will not require the new large hydrogen tank needed in all future variants. This means the first prototype should easily be ready to make its first flight by the end of 2025.

3. When this occurs, if not before, the energy sector will conclude that there is no longer a good reason to continue investing heavily in SAF. For a period, it will still be needed for flights longer than 6,000km, but Airbus and Boeing will become strongly motivated by the airlines to develop a hydrogen-powered blended-wing airliner that can provide a range of up to 12,000km.

4. The UK’s FlyZero programme should now concentrate on designing a large blended-wing airliner capable of zero-CO2 flights of up to 12,000 km. The target date for its first flight could be as early as 2033. Cranfield University has already worked extensively with Boeing on blended-wing scale prototypes. Perhaps we will see a Boeing 888 based on a British design?

5. Airbus’s new Zero Emission Development Centre in Filton, UK, will have a key role in ZEROe, and is already working on whole system design and cryogenic testing.

6. Because flights of over 6,000 km will represent less than 25% the total CO2 output of aviation there seems little reason to start investing heavily in SAF if it is going to be completely obsolete by 2045. There are no other SAF applications, so once hydrogen airliners have a range of up to 12,000 km there will be no need for more SAF. Consequently, from a climate perspective it now seems that the large sums currently being promised for SAF production could be spent more effectively elsewhere.

7. The big problem now looming for Airbus and Boeing is the gap between the airlines reducing their orders for conventional aircraft and taking delivery of their first hydrogen airliners. The current apparent lack of urgency being shown not just by Boeing but also by Airbus seems to suggest they haven’t yet realized that the US Department of Energy’s target set in 2021 for the cost of hydrogen to reach $1 per kilogram by 2031 is now likely to be
achieved. Hopefully, we will soon see both Airbus and Boeing set new objectives which reflect the fact that cheap and widely available hydrogen is going to be the norm beyond 2030. An “order gap” now seems inevitable; Airbus and Boeing need to make sure it is as short as practical, which they are not doing yet.

8. We need to keep flying, despite “’light shame’, because a real solution is on its way soon, and the airlines need our money to be able to afford to bring us relief. So you will now be able to explain to your fellow passengers why they can already feel less guilty!

This article is follow-up piece to an aviation article on the same subject published in September 2021

Read more:  Large hydrogen-powered airlines could be in service in 2030

About the authors

Chris Ellis is a systems engineer, mechanic and writer, who obtained his Private Pilot’s Licence 55 years ago. After 10 years working for IBM and another three working for the UK Government, Chris held various senior roles in telecoms until concentrating full-time on limiting climate change.

Aeronautical Engineer John Coplin was chief designer for Rolls-Royce RB211, the parent of the Trent family of engines powering the wide body jets. He was former director of technology and director of design for Rolls-Royce, former visiting professor at University of Oxford, and later at Imperial College London. He served as UK Advisor to the President of the Republic of Indonesia, a distinguished Engineer,  Prof Dr Ing B J Habibie.