Universal Hydrogen wants to enable zero-emissions commercial aviation by tacking the two biggest challenges: creating a distribution infrastructure and kick-starting demand for hydrogen. So the startup plans to build a logistics system and modify regional aircraft to use the zero-carbon fuel.

To discuss the company’s plans, technology editor Graham Warwick is joined by Universal Hydrogen’s co-founder and CEO, serial disruptor Paul Eremenko, along with Andy Marsh, CEO of fuel-cell and green-hydrogen producer Plug Power, and Roei Ganzarski, CEO of electric propulsion developer MagniX.

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Below is a rush transcript of Aviation Week’s January 22, 2021, Check 6 podcast.

Graham Warwick:

Hello there and welcome to this Aviation Week tech talk. Hydrogen is the talk of aviation at the moment, and there are many, many ways it appears that we could get hydrogen into aviation. But one of the first companies that is taking on that challenge of bringing hydrogen to aviation is Universal Hydrogen, and today we've brought you together the leaders of the team behind what Universal Hydrogen is trying to do. Universal Hydrogen is led by Paul Eremenko. He's co-founder and CEO. Paul was most recently the chief technology officer at United Technologies. Before that he was the CTO at Airbus. He was also the founding CEO of Acubed, which is Airbus's Silicon Valley innovation center. But before joining Airbus, and you're going to see a bit of a pattern emerge here, before joining Airbus he was director of engineering at Google's Advanced Technology and Project Organization, and before that he headed the Tactical Technology Office at DARPA, the Defense Advanced Research Projects Agency. If anybody knows Paul and Paul's reputation, he is a disruptor and Universal Propulsion is his latest venture to disrupt aviation.

So, he is joined - Universal Hydrogen is joined - by two key suppliers, and we have the leaders of those companies here today. So, Andy Marsh is president and CEO of Plug Power, which is bringing hydrogen fuel cells from concept to commercialization. Andy was instrumental in identifying that material handling - forklift trucks, things like that - was the first really commercially viable market for fuel cells. The fuel cells from Plug Power are used in warehouses by Amazon, Walmart and many others now. And the third member of our panel today and the third key member of the team is Roei Ganzarski. He's the CEO of electric propulsion pioneer and developer MagniX. He's also the executive chairman of electric aircraft developer Eviation, which is another company that's changing aviation as we know it. He was previously president and CEO of a company called BoldIQ, which developed a real-time schedule optimization software.

I actually first met Roei because BoldIQ came out of DayJet, which was an air taxi operation that Ed Iacobucci founded and it needed this incredible real-time optimization to make this air taxi system work. That became BoldIQ and I first met Roei. Roei now is running MagniX, which has really taken the lead in electric propulsion, powering the Beaver, the Caravan, and now with working with Universal Hydrogen. So, we're going to go to each of them in turn. I want to start with Paul. You've done many disruptive things in your career. Why hydrogen and aviation?

Paul Eremenko:

Well, thanks Graham for hosting this conversation. Look, CO2 is a problem and it's a serious problem. I've been in this industry my entire career. I'm very proud of the accomplishments of this industry. We're supposed to be on the bleeding edge of innovation for the human species, but aviation has no credible roadmap to meet the obligations and commitments of the Paris Agreement. So, the decarbonization roadmap that the industry has is sorely lacking, in my view. I'm passionate about making this industry a green and sustainable one. I've been, as you mentioned in my bio, I've been on the inside of a lot of the major players, both on the propulsion side as well as on the airframe side, and I know it's tough. We've tried a lot of different things in the course of my career, and of course the industry has been doing it for many other decades, including things like biofuels and synthetic fuels, batteries, et cetera.

Paul Eremenko:

None of those things are going to get us there for a variety of reasons that we can dive into later. Hydrogen is probably the only solution that the industry has to meeting the goals of the Paris Agreement and really making meaningful steps towards decarbonization. The reason for that is that, look, aviation is an extremely weight sensitive application. Hydrogen is an extraordinarily weight efficient energy carrier. In fact, it's the most weight efficient energy carrier of any fuel other than nuclear fuels, and I don't think we're putting nuclear reactors on airplanes anytime soon. Of course, we're not the first to have this realization.

This is not huge news. First manned hydrogen airplane flew in the '50s. The Soviets flew an airliner in the 1980s, the Tupolev Tu-155, on hydrogen. So, it's been a long time coming. What is new, though, is the advent and the maturation and coming in into its own of PEM, the proton exchange membrane technology, which is used both for water electrolysis to produce green hydrogen, to break water down into hydrogen and oxygen and then capture that hydrogen, as well as the reverse process, which is the fuel cell, which then takes the hydrogen, takes oxygen from the ambient air, and produces electricity, right? The maturation of that technology, the reduction in cost, the increase in efficiency, and of course Andy has been a pioneer in this field and can talk much more about it. That’s what's new and that's what's going to make hydrogen more affordable to produce and get it on par with jet fuel here just in a handful of years, by the mid 2020s, in terms of cost per unit energy.

It also enables a fuel cell electric powertrain for the aircraft, which is significantly more efficient than a standard combustion engine, whether it's a turboprop or some other kind of engine architecture. Because the electric-chemical energy conversion process is just inherently more efficient than a thermodynamic one. So, that's the train of thought, the logic that's led me to hydrogen, led my co-founders and me to hydrogen. And then the goal of Universal Hydrogen is really to complete the hydrogen value chain and make this real in aviation as quickly as possible. Because again, we got to move, right? It's not enough to have a 2050 net zero goal. The Paris Agreement, the 1.5 degree global warming scenario, puts us on a trajectory and we got to be on that trajectory pretty soon here. So, we need to be decarbonizing this industry now, and certainly by the mid-'20s and by the 2030s, and so that's our goal.

There's two places where the hydrogen value chain for aviation is broken, and so what Universal Hydrogen is doing is tackling those two segments which are necessary to complete it. One is in the actual carrying of the hydrogen molecule from the point of production, which Andy is doing, the production of green hydrogen. And then we are taking that hydrogen. We're putting it in capsules, these modular capsules, which are a very efficient way of moving hydrogen around and makes hydrogen essentially dry freight. So, we can make it compatible with the existing intermodal freight network, meaning that we put these capsules in shipping containers and those shipping containers go on trucks. They go on trains. They go on ships anywhere where the existing freight network can go. That intermodal freight network is probably the most efficient way that we as a species have of moving stuff around the earth.

That makes for a very cost-effective and very, very low capex - very low capital investment requirement - way to create a very agile way of distributing hydrogen to any one of the 17,000 commercial airports in the world. The second thing that we're doing is we're working on a hydrogen powertrain, a fuel cell electric powertrain, and here Plug Power is working on the fuel cell with us. So, we're taking their flagship ProGen line of fuel cells. We're working together to lightweight that and get it certified for aviation use, and we're working with Roei on one of the biggest electric motors - what will probably be the largest in terms of power level electric motor to fly - which is a 1.6 megawatt motor, which allows us to power a regional class aircraft. So, something that is commercially meaningful, 40 to 60 passengers, Dash 8, ATR 72 class aircraft, and do so in the near term, right?

Those are the two things that we're doing - developing a hydrogen distribution, hydrogen logistics system for airports using these modular capsules that then go into the aircraft and developing a hydrogen powertrain, which will be a conversion kit for regional aircraft that we expect to have certified and in service by the mid 2020s and start meaningfully decarbonizing an important segment of aviation, a growing segment of aviation, which is regional as a springboard to larger airplanes, like the single aisle in the 2030s and other segments like urban air mobility and eVTOL as those segments mature.

Graham Warwick:

Thanks, Paul. So, over to you, Andy. Are fuel cells ready for aviation? Obviously you're on the production side, is green hydrogen ready for aviation?

Andy Marsh:

Graham, thank you for having me today, and the big answer to that question is yes. So, let me take a step back. Many of us, not only Plug Power but people like Toyota, Honda, Ballard Power, have been in the wilderness for 20 years developing this technology to get it ready for prime time. Plug Power has had extensive experience. Our units have operated over 600 million hours. As you mentioned before, we're doing it with people like Amazon and Walmart. Just to give you a feel for how prime time it is, 30% of retail food during the COVID crisis in the United States was actually moved using fuel cells at one point in time. And then you start thinking about, when you talk to the Amazons and Walmarts and their long-term sustainability goals, they're really looking at fuel cells for business to business vehicle applications on the road.

The reason very much as Paul described for aircraft, is the gravimetric density. It's lightweight as well as the fact that fuel cells have a much, much higher power density than batteries. So, you add that up, are fuel cells ready for prime time? Absolutely. if you look at work that's being done by the Global Hydrogen Council, which represents over a hundred companies involved in this field around the world including very much household names like Shell Oil, Total - I think folks you've probably heard of - and when they've looked at this, they say hydrogen and fuel cells will be cost competitive versus internal combustion engines by 2027, 2028. From our experience, every time we doubled the number of units in the field, we've seen our product costs go down by 25%. But let me also tackle green hydrogen. Plug Power has plans to build out over a hundred tons of green hydrogen capacity in nine states just in the next couple years, and that's using electrolysis and low cost renewables.

When you start thinking about renewables in the range of 4 cents a kilowatt hour - and I think to most of the people listening to this podcast those numbers aren't outrageous because you see deals going on around the world at 2 to 3 cents a kilowatt hour - hydrogen green hydrogen can be provided for under $3 a kilogram. A kilogram's equivalent to, if I lived in the gasoline world, two gallons of gasoline. So, you look at the cost trajectory. You look at the environmental footprint. You look at the real experience not only Plug has had with fuel cells, but many other companies, the technology is here, now and ready. Before I stop, I just want to mention what I really love about Paul's business model is it's practical. Now, with Plug, I approached a business asking "What can you do first and be successful?" I think Paul's approach to aviation allows hydrogen to happen sooner. I think Paul's targets of 2024, 2025 are realistic because he's using off the shelf building blocks to make it happen.

Graham Warwick:

Thank you, Andy. That's interesting. So, Roei, you're already a pioneer in electric propulsion. As I said, you've got aircraft flying with big motors. What does becoming part of what Universal Hydrogen is trying to do mean for MagniX?

Roei Ganzarski:

Well, it's the next step of the evolution of this revolution. One of the things that are so common between Universal Hydrogen's beliefs and MagniX's beliefs is that it's really about fixed-wing aircraft taking off from an airport, landing in an airport and doing so with a meaningful number of people or cargo flying between 50 and 1,000 miles. It's not about trying to turn the 777 or A380 electric, and it's not about trying to buzz two or four people in between the high rises of a downtown metroplex to avoid traffic. Those two things one day will happen, but they're very long away for various reasons, technology just being one of them. The beauty of focusing on the middle mile fixed-wing aircraft is that's what makes it practical and available and real in the near term. So, that's one thing.

The second is we're also true believers in what Paul is doing and Universal Hydrogen are doing: let's start with the simpler way of doing things. Let's take a proven aircraft that we know can fly, in this case the Dash 8. Everybody knows that aircraft. And let's just change what turns the propeller. That's a lot simpler than taking something from scratch at this scale to take it forward. So, we are completely on board with everything that's being done and very excited to be part of it. Now, let's put the propulsion twist on it. As you mentioned, MagniX is really focused on propulsion, electric propulsion for electric aircraft, specifically commercial electric aircraft. The smallest aircraft we've already flown and continues to fly is the de Havilland Beaver, an amazing aircraft we converted together with Harbour Air. That uses a 750 horsepower or a little over half a megawatt propulsion system.

Then we started flying the Caravan, a Cessna Grand Caravan, also using over half a megawatt propulsion system, all electric using batteries. Now for an aircraft of size of the Beaver, of the Caravan - five, nine passengers - batteries work. While they're not where we want them to be for full adoption, mass adoption, for niches of 100-150 miles they work for these small aircraft where hydrogen won't work for such a small aircraft. Conversely, at an aircraft of real regional proportions - 40, 50, 60 passengers, like what Universal Hydrogen are looking at - batteries won't work. They're not the solution. You don't have enough power in batteries to be able to pull that off. Whereas hydrogen is the perfect solution for it. You take a Dash 8-300 that's a 50 passenger plane. You put it powered by hydrogen, and now you have a 40 passenger airplane.

40 passengers is significant. We're talking about Part 25, real airline flying. So, anyone who two years ago was a naysayer to electric and said, "Ah, this will never work." Then we started flying the Beaver. It's like, "Well, okay. But the Beaver is a niche. It's only five people. It was a seaplane." Then we did the Caravan. "Oh, okay. Well, that's only nine people and it's a Caravan." Now we're talking about 40 people in a Dash 8. People are running out of arguments to say no. Now, whoever doesn't want to believe it will continue to not believe it. But whoever wants to believe it, we're way beyond the point of no return. There is no aborting takeoff. This thing is going forward and is going to revolutionize the world. Now, in terms of the propulsion itself, we have already flown the over 500 kilowatts. So, it's a 640 kilowatt propulsion system, motor inverters, the cooling, the whole thing. It's proven. It's flying now. It's on its path to certification, in fact.

We have our means of compliance out there. We have our special conditions for Part 33 certification out there. We are on track to get this certified. For the Universal Hydrogen propulsion system, although it's 1.6 megawatts and not 640 kilowatts, the building blocks are exactly the same. So, we have minimal risk in what we're doing here because we're taking the tried and proven flying propulsion systems and expanding them, scaling them in a way that, by the way, was already planned to be scaled because we took our 280 kilowatt motor, scaled it to 560 and 640, and now we're scaling that to 1,600. And so the risk here of being able to do this is minimal. It's done with proven technology and technology that was designed from the ground up to be aerospace. So, we are not taking a car electric motor or inverter and trying to make it work. We're taking aerospace-grade propulsion systems that were designed to fly at 30,000 feet unpressurized, and we're putting them into an aircraft that will do the same thing. So, from that perspective, I don't think there's a better group of companies who can make this work.

Graham Warwick:

Amazing that, as you say, it's this practical approach to making this happen. So Paul, there is a tremendous amount of skepticism around hydrogen and a lot of that is focused on the big airplanes, how did we ever get it to the Airbuses and the Boeings of this world? But one of the big areas of skepticism is around the infrastructure, around the production of the green hydrogen, about getting it to the airports. I mean, how big an issue is it? When you look at this problem, how do you tackle that problem of how do you produce enough and everything like that?

Paul Eremenko:

I should probably let Andy comment on the production scale, right? He mentioned the incredible ramp up that Plug Power, and I should say that the industry writ large, has in terms of increasing emphasis on green hydrogen production over the coming years. So, we do not anticipate there being a production choke hold to the regional market. Certainly when you start talking about the single aisle aircraft market, which flies most of the revenue passenger miles in aviation, in the 2030s it's a couple of orders of magnitude beyond that, but it's also a fair ways away. So, we're talking again about a 2025 kind of entry into revenue service and we don't see a supply problem. In fact, as Andy alluded, in terms of the cost of the supply of green hydrogen, we think it will be at equivalence or better than the cost of jet fuel, and certainly better if you start including carbon offsets and carbon pricing into the cost of jet fuel at that point.

So, economically it makes sense. What is missing is, you're absolutely right, is the distribution infrastructure. Particularly for regional carriers, which may fly just one flight a day into a remote airport. Getting hydrogen to that airport is a challenge. That's the challenge that we're solving because we recognize that that's been the key impediment to completing the hydrogen value chain and making it real for the aviation vertical. I think the theme here that you've heard in everybody's remarks is that is a very pragmatic approach. So, nothing exotic, no custom pipelines, no custom vehicles to move the hydrogen around. A capsule. There is some cleverness in the capsule design, both to make it lightweight because that's the capsule that also goes into the aircraft and to make it aerospace certifiable from the ground up.

So, it is not a composite overwrapped pressure vessel. We do foresee challenges in certifying a standard composite overwrapped pressure vessel. We have a layered approach with a separation of functions across those layers, which yields something that's lighter and that's designed for certification. And then that capsule goes into a semi-truck or on a train. It gets to the airport. It gets unloaded, and is popped into the aircraft using existing cargo loading equipment. So, at some of the more remote airports that might be a forklift. At the bigger airports it would be something like a scissor lift that you would use to load cargo into the aircraft.

So, there's no transfer of hydrogen from container to container or vessel to vessel. The hydrogen stays in the capsule from the point of production to the point of consumption inside the aircraft. So, there are no losses. There are minimal safety issues. Because the hydrogen doesn't get transferred and it pops into the aircraft with a quick connect and then gets removed once it's depleted at the end of the flight and goes into a reverse logistics chain. So, again, the emphasis is on simplicity, minimal capex, and a pragmatic approach to getting to certification and into revenue service as quickly as possible.

Graham Warwick:

So, how are you taking the approach to rolling this out? Would it be a regional approach? Would you go to a place that's a hydrogen valley which is already embracing hydrogen, or to Scandinavia where they've got lots of renewable power, or do you actually ship this hydrogen from Plug Power somewhere in the US to wherever it's going to go in the world? I mean, how do you see this deploying?

Paul Eremenko:

So, we are taking a region by region approach within the network of the regional airline. We would identify hydrogen offtake points and then transport the hydrogen within that network. Obviously, the number of production sites is going to continue to increase and probably to increase very, very rapidly, but it is a region by region strategy. I think maybe Andy, you might comment on your region by region extension strategy for green hydrogen production.

Andy Marsh:

Sure. Before I even go there, Paul, I'd like to really emphasize, I would almost say there's a gold rush for building hydrogen facilities around the world. So, you look at Europe where 20% of the money for recovery from COVID is actually geared towards hydrogen. Between Europe and Northern Africa, they're looking to have 80 gigawatts of capacity in place by 2030. When you start looking at the world energy, there were projections by people like Goldman Sachs who were saying 18% of world's energy will come from hydrogen by 2050. Hydrogen during the next decade starts becoming a ubiquitous fuel and, most important, it's a green ubiquitous fuel, and it's people like Shell Oil, Plug Power, and many others who are driving this.

For us here at Plug Power by the end of 2023, we're looking to have over a hundred tons of green hydrogen capacity spread into five regions of the United States. We actually know how to move that hydrogen around. We do it today. We use 40 tons a day ourselves at Plug. When I look at long-term, we're beginning to put plans on the table to be much, much bigger than I've just mentioned. Look, there's other people like NextEra, like Total, like all sorts of folks who are looking to build out green hydrogen plants across North America.

Graham Warwick:

So, back to you, Paul, on taking this fuel cell technology. When you went into looking at fuel cells and their suitability for aviation, were you convinced or confident that you can take Plug Power's ground-based systems and produce a really competitive aviation power plant, and that you can see a technology runway in front of you where you can continue to improve that, the way that turbine engines have improved over the years, and grow it in a way that you can go to bigger sizes of aircraft?

Paul Eremenko:

Yeah, absolutely. Look, the two key figures of merit for aviation hardware are weight and certifiability. Weight and safety. We have a very aggressive joint effort with Plug Power to lightweight their terrestrial fuel cells for aviation applications. This doesn't require any exotic material substitutions, or any invention in particular. It's a pretty straightforward engineering effort just to take weight out and customize it for the kinds of considerations like crash loads, et cetera, that you might have in an aviation application. And then the second aspect is safety and certification. On this front, it's actually not an issue of first impression for the regulators or for the industry. The industry has been talking about fuel cell AP use for some time, and the regulators have looked at it.

There's actually an SAE standard for aviation fuel cell safety. So, that's something that's been thoroughly socialized within the industry. I don't want to diminish the challenge, but for the fuel cell in isolation, I think the certification path is clear. As Roei mentioned for the motor in isolation, the certification path is very clear. An end to end powertrain is going to have new failure modes, new coupled interactions between those devices, and that's the hard engineering work that we have ahead of us in the next couple of years. But we have a very detailed plan to do that. We've engaged with the regulators on that plan. Again, we know how to do this. I think we've assembled the best possible team in the world to get this done. So, we are very confident in being able to bring this to market as a very economically competitive, but also a green product, which I think will be very appealing both to the flying public, to the passengers, and to the governments around the world.

Graham Warwick:

So Roei, I wanted to quickly come to you. Obviously, you're a pioneer in electric propulsion. You've been talking to the potential operators for some time now, and you'd been talking about battery powered airplanes, and the inevitable compromises that the operator might need to make in how they operate in order to take advantage of that. When you now bring fuel cells, zero emission fuel cells, into the equation here, what's your sense when you talk to these folks about their willingness to say, "Okay, I'll lose a few seats. I'll take my range down, but I will get zero emissions as the result of that. I will get carbon zero aviation out of it"? What's your sense of the willingness of the customer base to make those decisions to change how they operate in order to get to carbon zero?

Roei Ganzarski:

Well, that's an interesting question. I'll start with a small correction. When we talk to customers, we don't talk about batteries on a plane. We talk about electric aircraft. They might be powered by batteries. lithium-ion, lithium-sulfur, solid state. There's all sorts of different chemistries coming about. It might be fuel cells. I also like to joke and say, "There might be two gerbils turning really fast on a wheel creating electricity." Where the electricity comes from, from the operator's perspective, is less important. What it comes down to is lower operating costs, higher reliability, and a green, clean aircraft. The aspects of environmental awareness that are happening in the world that started five, 10 years ago, but now are really taking hold - especially if you look at the new incoming administration, if you look at what's going on in Scandinavia, if you look at what's going on in France, environmental awareness is nothing to be kidded about or nothing to be sideswiped.

This isn't about whether someone believes or not in global warming or climate change. It's really about the understanding of every person today in the world that emissions are bad. They're bad for your health. They're bad for the environment, et cetera. Aviation is one of the only industries in the world that somehow gets away with not tracking CO2 emissions, with not paying taxes on their CO2 emissions. Cars are already constrained. Trucks are constrained. Ships are constrained. For some reason, airplanes get away with whatever they want to. That is coming to a change. Not because of what we are saying or we're doing, but because governments and the people are figuring out that's not good anymore. From an operator's perspective, their main question is, "Will I still make money as an operator operating these planes? Will I still be able to do it certifiably and safely? Will I still be able to provide the services that I provide?"

The answer to your question, Graham, with fuel cells for all of them is absolutely. The question of safety is never a question because if an alien tomorrow showed up on planet Earth, and we were to tell that alien, "We're going to put you on this tube here filled with one of the most combustible liquids found on Earth. By the way, we're going to ignite it in order to create thrust," that alien would laugh at us and go back to whatever planet they came from. Yet we all do it every single day because we trust that the companies who set this up, the regulatory authorities that approved it, did the right thing. For now, batteries, hydrogen fuel cells, this is just new and so we're thinking, "Oh, is it safe? Is it not safe?"

Of course it's going to be safe by the time it's certified. That's not even a question. The operators who are all in this industry understand that once it gets FAA approved, we're past that. When it comes to giving up 10 seats on a 50 seat plane but being able to tell every passenger, "If you choose to fly my airline on a hydrogen aircraft, you will know that you've contributed nothing to environmental impact that's negative, you've contributed nothing to emissions, rather you've paid your ticket and now done something better for the world while still traveling," that is a huge competitive advantage that all the other airlines who stick to primitive technologies will not be able to compete with. From that perspective for the airlines, this is a slam dunk. Now we just have to achieve it and execute on it.

Graham Warwick:

Wow.

Paul Eremenko:

Graham, can I chime in and follow up on Roei's very eloquent and passionate response to you there? So, the economics work, right? So, yes, there is clearly a tectonic shift in what passengers want. There's clearly a very significant shift in what governments are going to force airlines to do. But most importantly, the economics just make sense. So, on a cost per available seat mile [CASM] or a cost per available seat kilometer basis, which is the direct operating cost of unit economics for the airline, we are competitive at the aircraft level. It will be equivalent economics by 2025 at the point at which we enter service. There's a couple of factors that go into that CASM calculation. You're right to point the fact that there's a loss of two rows of seats in order to accommodate the hydrogen.

You can't put hydrogen in the wing. The hydrogen's got to go in the fuselage. You do lose a little bit of fuselage volume so you lose two rows of seats. That's in the cost per available seat kilometer. That's in the metric. That's taken into account. The countervailing effect is that the powertrain end to end is more energy efficient, and that was my point about the thermal-chemical energy conversion. You can get higher efficiency out of it combined with an electric motor, which has incredibly high efficiency, in the 90% range. It is not limited by the Carnot Limit on the efficiency of the thermodynamic cycle that jet engines have. You get better efficiency. You get lower maintenance costs. A fuel cell has no moving parts. It has a very stable thermal environment.

Electric motor has many, many fewer moving parts. So, we've done some modeling together with Plug Power and MagniX on what does the maintenance cost for this powertrain look like, and it is a significant improvement over a turboprop engine. The third piece is the fuel cost itself. We've already talked about the fact that on a per unit energy basis, it'll be at parity by the mid-2020s with jet fuel, and certainly if you include carbon offsets and carbon taxes.

Roei Ganzarski:

By the way, Graham, tell an operator of a Dash 8 or an ATR that hot and high is not a big an issue anymore. Because as opposed to internal combustion engines that, as you climb or as temperature goes up, air density is reduced and thus the power out of the internal combustion engine that requires that air is reduced, the electric propulsion system isn't reliant on air and so temperature and altitude are not an impact. And so the performance of the aircraft at those same economics that Paul is talking about is much better.

Graham Warwick:

Okay. I think actually, Roei, you were the one who said it best, that the naysayers have had to keep changing what they say nay about as we go forward. We are now into this with you guys. We're into this phase where they have some things they're saying nay about, but as every day goes by it's getting harder and harder to say that. So, I think I'm going to wrap up here, guys. You've given us all a lot of detail, a lot to think about, so I really want to thank you very much, I must say. So, I hope you enjoyed this Aviation Week tech talk and look forward to the next one. Thank you.

Roei Ganzarski:

Thank you very much.

Paul Eremenko:

Thanks, Graham.

Andy Marsh:

Thanks, Graham.