Welcome everyone. Thank you for joining us today for the Races Zero's November Dialogues Transport Day. My name is Kevin Soupley, and I'm the project lead for the World Economic Forum's Clean Skies for Tomorrow initiative, our global coalition working to achieve net zero aviation by mid-century. I work on the forum's Future of Mobility team, and in partnership with our Races Zero partners, we are your hosts for this session. Over the next hour, we'll be discussing building a path for net zero aviation together with leaders from across the aviation value chain who are driving real, tangible progress in transforming this hard to obey sector. 2020 has been a bit of an unusual year. The impacts of the COVID-19 pandemic have been devastating and have brought us to a strange new normal in our way of life. Hopefully, we'll soon be able to resume activities that we all miss, dining out, travel, meeting in person, though it may be some time yet. Aviation has been particularly hard hit by this crisis. This is, in fact, the worst economic crisis in aviation's modern history. Passenger volumes are down over 60 percent. Industry revenues have dropped over 400 billion US dollars just this year alone. We don't yet know when the crisis will end. But indeed, aviation brings tremendous societal and economic value, delivering international diplomacy, travel for business and leisure, and closing the distance between loved ones. We're working on a return to the skies as soon as possible, but aviation is also still a polluting industry. So while we struggle to find solutions for the pandemic and climate change remains a threat and the time for action is quickly passing, so that's why, both at the forum and across the industry, we're working to adjust these global challenges with global solutions. Amidst all of this, there's room for optimism. Even as they face significant job losses and operate on skeleton staff, we've seen a doubling down of commitments across the aviation value chain to help transform the industry to one that is more sustainable. Just over the past few months alone, we've seen tremendous progress with voluntary declarations from the 13 airlines and the One World Alliance to be net zero by 2050 and creative partnerships with aviation consumers like Microsoft to accelerate the industry's energy transition. So that brings me to the topic at hand today. Is it possible to supply sustainably now? If not now, when? What are the technologies and collaborations happening now to get us to where we need to be? So let's get started. Thank you for joining us. First up, we'll hear from Charles Perry, aviation lead on the COP26 climate champions team to provide opening remarks about the November dialogues COP26 and Aviation Race to Zero. Charles, over to you. Thank you very much, Kevin. Hello to each and every one of you. It's great to be here today on this important occasion. Welcome to the race to zero. Yes, I'm Charles Perry. I'm the aviation lead on the COP26 climate champions team. And I'm also founder of a business called sustainable future for all. I want to tell you I recently got inspired and got to know an amazing woman. Her name is Dr. Catherine Katie Coleman. She's an astronaut. She lived at the space station. She flew the shuttle. And she really inspired me in these difficult turbulent times in the last few months.  Sailing the stars, navigating in space. Well, now we have to navigate to cleaner, clearer skies. We are on a voyage, a journey to a more sustainable future. And we need each of you to join us to become not astronauts, but zero laws. Zero laws leave no footprint. We have to smash this or as Taylor Swift or will I am might say we have to kill it. Why? What is it? Pollution.  And I'm not just talking about carbon dioxide pollution. I'm talking about all greenhouse gas pollution. So today, please take your organizational hats off, whether you're on the panel, whether you're in the audience, just be yourselves as individuals. And think of whether you can commit to becoming a zero naught personally. I believe we can get to net zero by 2050 for a hard to obey sector like aviation. I know we must get to net zero by 2050 or earlier. And I think we will get to net zero by 2050, but only if we collaborate radically. No longer divisions and turf wars, but united we will succeed divided we will fail. We've just seen an example of leadership to unite versus divisions in a big country. This today is the rest of zero. Let's please folks ride these winds together and thank you for making the time to be with us. Thank you, Charles. Next, I'm pleased to introduce Judson Altoff, Executive Vice President for Microsoft's Worldwide Commercial Business. He's joining us today to remark on Microsoft's industry leadership in investing in sustainable aviation fuels as a method of reducing the company's environmental footprint from travel. He's joining us over a recorded video given the time difference with Seattle. So let's hear from him now. I'm Judson Altoff, the Executive Vice President of Microsoft's Worldwide Commercial Business. And in my personal time, I'm an aviation enthusiast. In fact, I'm a private pilot with an instrument rating. And so this is a topic, frankly, that is both near and dear to me professionally, as well as personally. Look, the scientific consensus is clear. The world confronts an urgent carbon problem. Humanity has released more than 2 trillion metric tons of greenhouse gases into the Earth's atmosphere since the start of the first industrial revolution. Over three quarters of this is carbon dioxide, and it is simply more carbon than nature can reabsorb. Additionally, humanity pumps more than 50 billion metric tons of greenhouse gases into the air every single year. If we don't curb our emissions, temperatures will continue to climb, and science tells us that the results will be catastrophic. Earlier this year, Microsoft announced several sustainability commitments. We became net zero and net negative in our carbon footprint in terms of our commitments for the year 2030. And by 2050, we committed to erase the entirety of our carbon footprint since the inception and founding of the company itself. As a part of Microsoft's carbon negative commitment, we have a goal of reducing our supply and chain emissions by over half by the year 2030. This includes our employee air travel, which currently accounts for roughly 400,000 tons of carbon each year. Business travel has been one of the areas that is effectively the long pole in the tent, if you will, in terms of trying to solve for sustainability. It's easy to do certain things in the equation of pursuing being net zero and net negative carbon, but travel and certainly air travel is one of the more difficult ones. So this year, we decided that we would make an additional commitment relative to sustainability. And whilst right now in the time of COVID, not many folks are traveling, we do expect business travel to return to significant and substantial levels. To address the challenge, we formed partnerships with airlines like KLM and Alaska to invest in sustainable aviation fuel for our business flights. This past October, Microsoft partnered with KLM to purchase an amount of sustainable aviation fuel equivalent to all flights taken by Microsoft employees between the United States and the Netherlands on KLM. And just this past month, we built on this momentum by announcing a partnership with Alaska Airlines to acquire sustainable aviation fuel and the equivalent for the total amount of fuel we would otherwise burn on Alaska Airlines for our busiest routes, in fact, our most common routes for business travel between Seattle and San Francisco, between Seattle and San Jose, and also Seattle and Los Angeles. We're excited about this because whilst COVID has created a bit of a relief on business travel, we expect to continue to travel in the future to engage with our customers and support them around the world. And we wanted to return to flight responsibly. Right now, sustainable aviation fuel is more expensive. And because it's more expensive, it's harder for energy companies to justify the production. And so you end up with a bit of a chicken and egg conundrum between supply and demand. In order to break this cycle and create a more effective flywheel for the ecosystem, companies like Microsoft need to step forward and make these kinds of commitments so that energy companies can see the demand signal and produce more sustainable aviation fuel. As production levels increase, so will flow the laws of supply and demand, and the costs will come down, making it easier for airlines like KLM and Alaska to purchase more sustainable aviation fuel. At the end of the day, it's more than just Microsoft KLM and Alaska stepping forward. It's about enabling a flywheel so that the entire ecosystem can step forward and make similar commitments, because effectively we're all in this together. This is something I'm genuinely excited about. I remember sitting in the Cleaner Skies Forum in Davos this past January, where many business leaders came together to discuss this challenge. And we highlighted how the private sector, how the airline industry, how energy companies all needed to come together with governments around the world to create this flywheel. So I'm very proud that Microsoft's been able to step forward and make this commitment. And I'm excited to see more and more companies join around the world. But this year has been certainly one of the most challenging ones for all of us to endure. It's been a very difficult business climate. Many people have struggled with healthcare concerns around the world. And so climate and climate issues have taken a bit of a backseat for many of good reasons. But the challenge of creating a sustainable future for our planet will be one that persists. And it will be one that we all need to come together to solve. So I'm excited about this step forward. And I'm excited to see what all of you may do to join in this important step for sustainability. Wonderful. Thank you to Judson for those comments. So without further ado, I'd like to hand things over to Wendy Woods, joining us as moderator for our excellent panel discussion. Wendy's managing director and her senior partner at BCG, where she serves as vice chair of their social impact practice. She's an influential voice on corporate strategy and is a thought leader on sustainability and rethinking business's role in society. So an excellent person to walk us and guide us through this discussion. Wendy, the floor is yours. Thank you, Kevin. And thank you, Charles, for setting us up so clearly in terms of the challenge before us today. I'm really pleased to be able to coordinate this panel today. I will tell you it's a topic I'm passionate about, not just because of my role leading climate for BCG with our clients, but because this panel and all of the individuals on it today are going to be the path for BCG to meet our net zero commitments. We've made some aggressive commitments about being net zero by 2030 by reducing our travel emissions and by neutralizing the remaining and ultimately going that negative beyond 2030. But there is absolutely no way we're going to meet those commitments without everybody on this panel. For BCG, being a global firm, three-fourths of our emissions come from airline travel. So I find this discussion today not a nice to have, but something we have to do and something that is incredibly timely and urgent. COVID has been a challenge in the world. It's taught us how we can do some things differently. But as Kevin set us up, we know that we will need to fly for our economy and frankly for our humanity. So I would love to pick up this conversation and let's get concrete and specific about how together collaborating, we can build a path to net zero aviation. Given we've got a great panel that really covers sectors in the value chain, I'd love to start on the technology end in terms of the infrastructure and the the planes. Let's begin. We've got Dave Smith, who's director of technology with Rolls-Royce. He's responsible for sustainability across all of their product lines. Now, some of me say, well, what does Rolls-Royce have to do with airlines? Well, they build half of the engines that go into all of our long haul planes. So very important part of the technology to getting there. Another person who's going to join us on the panel from the technology side is Jeff Engler. Jeff is the CEO of Ride Electric. And Ride Electric has committed to developing an electric plane, a 737, one of the ones we would all want to fly in commercially, right? An electric plane by 2030, pushing the timeline for that. We've got the infrastructure folk here. Dick Benchork is the CEO of Shipple Airlines, or sorry, Shipple Airport. He's been a leader in the ecosystem in the Netherlands and in the EU, pushing policy around blended mandates for inter-EU travel and really working to create that ecosystem that's going to help us all get to where we need to be. We have Jennifer Folgrom. You heard Justin talk about sustainable airline fuel or staff. Jennifer is the person who's helping us make that. As CEO of Lanzatec, they're working on waste to power, waste to fuel, sustainable airlines fuel. And we have Jonathan Council. He's the group head of sustainability for international airlines group. Jonathan is the force behind the One World Alliance commitment to net zero that we've all recently seen. So let's now move into the discussion of this esteemed group. Dave, I'd love to hear from you. I know over time airplanes have been getting more and more sustainable. I think each new generation gives us 20 to 25 percent efficiency. But are we hitting a wall there? Are we going to be able to continue to drive more and more efficiency with new generations of airlines? Or what is the move that you who build the components that go into our planes going to be able to contribute to net zero? We can certainly go further and we invest as an industry. I know our company invests about a billion pounds, which is probably a billion euros and a billion dollars at the moment as well in research every year to drive efficiency further. We expect by 2050 that aircraft overall will have delivered a 30 percent further efficiency improvement. So that takes the amount of fuel we need to burn right down if we change nothing else. And we need to do that because the challenge is enormous. It's possible if we all pull together. I'm very struck by Charles, the zero-naught. I'm going to become a zero-naught and we all have to work together. One of the things that struck me when we joined the panel is a lot of people know each other and they know each other because we've all been talking about this and working on this very hard for the last years because we know we have to work together. We need aviation traditional like Rolls Royce. We need to add the new. Jeff will talk about the new but we're we're inventing the new ourselves as well. We've got a big electrification of aviation business growing within the company today. We need oil and gas companies, the ones we have today and we need new ones like Jennifer is going to talk about the new fuels that we have to have to decarbonise aviation. And we need our colleagues, the airlines and the airports who actually get customers in and get people around the world and make the whole thing worthwhile. And then we need governments who are going to make the market and people like Microsoft who are making the market because this is going to be an immense undertaking for humanity. But we can see how to do it if we all come together. But but we do all need to come together. Thank you very much Dave. And Jeff, I'd love to turn to you now. You've committed to an electric plane and 2030 longer than we want. But coming up pretty quickly, how are you going to get there? What is the contribution of right electric? What do you think the potential is? And I'm curious because we heard in the introduction from Judson about the sustainable airline fuels. What do you think the interplay electric sustainable? How is that going to play out for us? That's a great question. Thanks for asking and thanks for having me. So the state of California announced that they're banning gas powered cars in about 15 years. And there's a reason why California didn't say all cars will use sustainable fuel. They said all cars have to be electric and it's because electric is better. It's just better for the environment. Simple as that. So we think for flights that can be electric, they should be electric. And then for flights that can't be, we think sustainable aviation fuels are the best solution. So there's a room for all of these technologies. Collaboration is the most important part of this program as other folks have said. We're focused on short-haul flights. Dave was talking about longer-haul flights. We think for the quarter of the aerospace industry that is short flights using 737 or A320 class airplanes, they should be electric and everything else should be sustainable aviation fuels. So for our group, we've got about a quarter of the industry, I think potentially less in terms of passenger miles, that is short-haul. We've got about pre-force that's long-haul. And what you're saying is the electric plane, the 737 ish that you're going to be developing would be for the short-haul component. We've got a lot of work to do with things like sustainable airline fuel for the long-haul. That's exactly right. Yep, exactly right. And so that's why we think there's a role for everybody on the panel. And it's not only the technology, it's also the airports, it's also the infrastructure. Everybody has to be working together. And we want to do our part in collaboration with everybody else. I think, Jeff, you've got a contract with EasyJet. How do you see your customer base? What do you see the uptake? Are you seeing demand? We talked about demand. Are you seeing demand? No, absolutely. There's demand not only from the airlines but also from the customers. We know that what the industry is looking for and what consumers are looking for is the lowest emissions travel possible. Nobody wants to stop flying, but they want to, or nobody wants to stop traveling, but they still want to do so in the most sustainable way. So we see it both from airlines and then we also see it from the end users as well. Okay. And in creating demand, obviously price matters. How do you see the cost of what you're talking about in terms of electric as compared to traditional fuels or sustainable airline fuels? That's a great question. So the nice thing about electric motors is they're much simpler than fuel powered engines. So the first thing is that from a maintenance and development perspective, the cost should be lower and then that cost gets eventually passed down to consumers. But then the cost of electricity and the cost of batteries are both coming down every single day faster than people might have expected. So we think eventually electric planes will not only be zero emissions but will be lower cost delivering higher profit margins for airlines and also lower costs for consumers. Thank you. Dick, I'd love to turn to you. As the CEO of Shipple, you've been driving a lot in the ecosystem. How do you see us moving and accelerating frankly to net zero aviation and the role that airports can play? Thank you very much. And thanks for having me. It's the biggest long-term challenge for aviation clearly. And I think you highlighted as others do the benefits of aviation, but we have to deal with sustainability. We have to deal with the carbon issue. That's the level of commitments, of course. And we as an airport and a group of airports, we do have a commitment, including to be net zero at the airport already by 2030, but then because we're not the biggest part of the emissions to contribute to cleaning up aviation as a whole. And we want indeed, and others will talk about that as well, to have a clear perspective and a clear commitment on net zero aviation by 2050. No separate table, no separate commitments for aviation. The sector suffered a bit from being quite early with its own commitment and then struggled a bit to catch up with Paris. I think that it is timely to do that now. And then it's all about the actions, of course, for ourselves. We have been trialing a taxi bot this year at the airport, so electrifying, pulling planes towards the runway and bringing them back instead of on their own motor. And we have been supporting, and that's really the, I would say, the line of attack for the coming decade, the development of sustainable aviation fuels. But it will be a first dedicated factory in Europe in the Netherlands being built. KLM supporting that, supporting that. And we'll have a pilot as well for the other side of the sustainable aviation fuels, the other parts around synthetic aviation fuel to be developed, because bio is not the only pathway, we'll need synthetic fuels, we need hydrogen for that. So in Rotterdam, we'll do a pilot with even direct air capture there. And then we're trying to work together because I hear that from everybody and it's really about moving the whole ecosystem in partnership. And we're doing our best here to get the fuel players on board as well. So sky energy, of course, dedicated here, but nestay, shell, unipair, and others, big developments potentially ongoing in the Rotterdam area around hydrogen, and I think building those coalitions and getting those players involved extremely necessary. My biggest concern really is we're in a race, in a race against time and in a race for skill, that's climate change. But then if we do, if we get everything right, we probably have a fighting chance, but then everything has to work together like clockwork, technology development, policy and regulation, investments, and it's really not yet. And that's where this policy and regulation dimension, the European Union, the Green Deal is so important, because we scatter gun at the moment with various measures and then yes, you get pilots and yes, you get a bit of taxation here and then you start to add cost there. Let's focus on the big moves. Let's focus on, for example, mandating sustainable aviation fuels, get pricing right, and make those big moves. And that clockwork is not there yet and that worries me a lot. What can we as a group, a process broad set of actors here do to enhance the policy and what I'll use the word regulation that we need to drive this to where it needs to be? First of all, be credible in terms of your own commitment and your own actions, of course, that's where it all starts. So everybody, we have to play our role that it's on the commercial side, the technology side, the infrastructure side, the deployment side. But secondly, have this type of dialogue as well with policymakers to get the policy part and the regulatory part right. Because if we don't do that, we'll see all kinds of first initiatives, first plant of this, first development of that. But how do we get beyond that? How do we get into this scale? And therefore the investments and the policy and the regulation and the pricing and the technology development all has to work together. So we need this dialogue as a sector between players, but with policymakers as well. Thank you. Jonathan, I want to turn to you as Group Head of Sustainability at IAG. I mean, you are the customer for the airplanes, of the airports, for the fuel that you buy. And you've made a very significant commitment with the one world commitment. Can you talk about what airlines think is possible, how they're going to get there? I hear all these nice words like, you know, zero-based routing and rethinking the way we operate. But you know, what can you do to get us there fast? Jonathan, are you on mute? I'm not. Hi. Hello. Good afternoon. Good morning. Good evening, everybody. And thank you, Wendy. Yeah, the one world announcement was a great project and a real example of, I guess, radical collaboration. It took about a year. All 13 airlines, though, are now fully committed. And the key was going back to the climate science, saying, so why net zero emissions by 2050? Link back to the science, because that tells you what you need to do. And it was great to be able to make the announcement that they can stop taking events. I had to say it was a truly collaborative event supported strongly by the one world team and their CEO, Rob Gurney, particularly. But now we're focusing on where next. One world won't solve the industry's climate change problem. We need the whole industry to come together. So we're hoping that will act as a spark for the rest of the industry to commit to these targets. Because once we get these targets, then we can start getting the policy mechanisms that can enable us to deliver these solutions. And we focus very much, as Dirk has said, on sustainable aviation fuels. So here in the UK, we believe 30% of all our fuels could be sustainable aviation fuels by 2050. We could have up to 14 plants here by 2035. And that will include Lanza Tech's great waste gas to jet fuel technology and our partner, Velocis, which takes waste materials and standard rubbish into jet fuel. But the absolute key is policy. We need policy. And I know Dirk has said that as well. So that's why we're working collaboratively with all of the major players in the UK to lobby our government. We need these policy signals now because our challenge is to attract investors to spend hundreds of millions of dollars to build these first of the kind plants. So one of the things we're very excited about is the UK government setting up the Jet Zero Council. So this is after a couple of years lobbying from the industry. So it's a real, it's another example of radical collaboration. So it's government led, it's chaired by two ministers of state, but it includes academia, NGOs, all of the major companies in the industry, and the oil companies. Basically, with the sole remit, how do we accelerate the industry's delivery of net zero emissions? So we're very excited about that. Well, thank you, Jonathan. Jennifer, I want to turn to you. As CEO of Lanzatech, we're hearing a significant amount of this depends on the SAP, the sustainable airline fuels in getting there. And it's a long haul flights are a large part of this. You're doing the waste to fuel and power. Tell us what Lanza can deliver. If I understand correctly, you've got customers committed to buying your output, right? That's right. So we are now building what is essentially a 40 million liter a year facility to take alcohol to jet fuel to SAF. And as that proves out, we actually have a parallel track to build three commercial plants that will get us to almost 400 million liters per year of SAF. And the target is by 2025 to be able to do that. And what I want to comment on is the way we did that is through some innovative financing. One of the problems we have when we're scaling up technology, and this gets back to the comment that Dick made, that we see a lot of things getting the first one. But how do you get the next three, the next five, the next 10, how do you diffuse the technology? And so the way we did it, because I spent a lifetime trying to cross the valley of death with new technologies, is we managed to get investors to agree that they would support building the first plant that I just mentioned that should be up and running at the end of next year. But if that succeeds, if that looks good, they're willing to then commit to investing in the next plant. And by doing that, by only bringing investors who agree to do both tranches, we're able to get ourselves on a path to scale. I do think governments really need to help. I see a lot of governments support the early stage. How do we do the first trials or the small plant, which is great. But it gets harder and harder once the plants get bigger and bigger and more expensive. And so we really need to fill the whole pipeline and support technologies as they get across. Once they've gotten across, let the market decide what the best technology is. But until that point where you've scaled and built a couple of commercial, you don't know the real cost. You don't understand the real potential. And you don't understand the environmental impacts, the true environmental benefits. So that would be my feedback. Jennifer, could we stay for a minute on this cost question? And one of the criticisms that I hear on SAF really is the cost and maybe to be specific, the cost at scale, right? I've heard a lot about, well, we can do a pilot in a small way and we can control the cost depending on where we source the waste and things like that. But how do we get to scale, be it with the biofuels and realizing that that's agriculture based and there's a whole value chain in harvesting those or even the synthetic as we talk about the PTO and the power to liquid. Can you talk to me a little bit more about the cost? I'm hearing criticisms from some people that SAF is about 10x the cost of a good offset. And I'd love to, it's an important component of how we get there for aviation. But what is your expectation about where the cost can get to? Yeah, and I think that's a great question, right? If the question is, is SAF going to compete in the next 10 years, and I'm using 10 years, not even a few years, with fossil based kerosene, I'm not going to hold my breath for that. Okay, right now kerosene is as low as it's going to get, right? Nobody's expecting the price of petroleum to go about 60 anytime soon per barrel, right? And that's going to make it very difficult for SAF to compete. However, I do believe that if we get past the next five to 10 years, the prices will come down. And the reason they'll come down is because as these new technologies scale, right, they scale at a point six factor, not a one to one per gallon, as you get bigger and bigger and bigger. But we need the technologies to have gotten to the next stages so that people have the confidence to build really, really big ones. You know, I'm talking about a billion gallons of production capacity at a specific site. If you can get there, then the costs will come down because the steel that you're putting in the ground will get less expensive. The other thing, and a lot of people, not just ourselves are focused on waste, because that's a feedstock that's readily available and inexpensive, right? In some cases, there's even a tipping fee because people want to get rid of it. So if you can do that, if you can really learn to access those feedstocks, again, the prices will continue to come down because your feedstock is normally 70 to 80% the cost of production. So as you can start to leverage those very cheap feedstocks, you will make real progress. I am really optimistic that if you think of it the way I do, which is caro plus carbon, that we will be competitive in the next five to 10 years if you think of it that way. But it has to be a cost of caro plus carbon and not just caro. Because I think the dynamics are such that the price of conventional fossils will keep coming down, demand will keep coming down, right? So these are things we need to factor into our equation. You know, we heard Judson talk articulately about the flywheel that can get going with customer demand and Microsoft's commitment to use sustainable airline fuels on some of their routes for their employees. Jonathan, we've heard talk about the expectation. But, you know, Jennifer, you talk about a scale of, you know, billions of liters or gallons. How do we get to that scale, right? Is it just accelerating that flywheel? What do you need to change with your customer base and your, frankly, your investor base to continue to accelerate to reach that kind of scale? Yeah, absolutely. And as Jennifer said, it's critical, get those first plants built. Once you get those first plants built, you quickly start going down the learning curve. And we're exactly with Jennifer. We think it will take five to 10 years. And then we'll have fuel that is cost competitive with fossil-based fuel with carbon prices. So for us, the focus, it's a sort of laser focus, get the first plants built. And that's where we need the policy support to help us do that. And there's a range of, and Dick has talked about mandates. And we think, you know, there is a role for carefully designed mandates to help provide those signals to our investors to give them confidence to invest that money into those first two or three plants. But Jennifer has also mentioned carbon pricing. And this is, this is really key. We need a global carbon price for our sector. And Corset is a great first step in that direction. And what we want to see is sort of a building on, on the good work we've got with that implementation of Corset, because that will eventually provide all the incentives we need to build the sort of third, fourth, fifth, sixth, and eighth plants. Thank you very much. Can I come back to some of the, the innovative topics we haven't talked about? I, I would love to hear someone talk to hydrogen. It's one of those things that I think people hold out there is a real opportunity. Is there someone who'd like to explain to us what that opportunity can be and how you may be playing in, Dave? Yeah, I'll talk about it. So you can use potentially, we can use hydrogen in aviation in, in two ways. We can, we can use it as a fuel for fuel cells to create electricity. And then it's sitting alongside the sort of battery technology we're talking about earlier for the short haul for the smaller platforms where it may be that using hydrogen and fuel cells competes with battery energy densities and might be more practical potentially. You can combust hydrogen in a normal, so almost in a normal car engine and certainly in a gas turbine. You have to check, you have to modify some parts. It's not the same engine. It doesn't just drop in like a, like a Saftas, like a Lanzatec fuel. We can just drop it in and our engines will work if it's blended. And we believe it'll work a hundred percent as well. And we hope to have news on that before Christmas as well. So that'd be great. But you can burn hydrogen in a slightly modified gas turbine if you can prove the safety and the reliability. That will get you up to sort of medium range potentially. It still isn't going to get you into the long haul. It's still not going to get you a transatlantic flight, we don't believe, but we don't see how that would happen. But, but that could well be one of the tools we need. We said earlier we've got to throw everything at this. There isn't one technique that's going to do it. Hydrogen could be part of it. There are some challenges. First, we've got to make enough green hydrogen in the world. And today we don't. We make brown hydrogen. We burn methane to make hydrogen, which is making the whole thing worse at the moment. So we've got to make a lot of green hydrogen. It looks likely that there will be a hydrogen economy globally. But the thing about hydrogen is you can do quite a lot with it. You can use it for heat, power, propulsion. So other people are going to want to use the hydrogen. And can we make enough green hydrogen to supply all of these uses? I don't know. Can you get it globally? So it's at every airport. So there's no point flying from one airport with a lovely hydrogen supply and landing at one without any because that's the end of that journey. And can you get a useful set of ranges? Or actually, if you're going to gear up an industry that creates enormous amounts of sustainable aviation fuels, which we all agree we have to do, and we all agree is possible, it's an immense effort, but it's doable, technically doable, economically doable, but difficult. If we're going to do that, then do we need another fuel? Do we need two sets of logistics? Do we need two sets of infrastructure? Do we need two sets of engines? Do we need two sets of aircraft? Can we afford that? And I think the jury's out on that one today. So hydrogen is very interesting. Everyone's investigating it. We should. We can't shut down any technological allies at the moment because we think we're going to need two, three, four. Even within SAFs, there isn't just one way of making SAFs. Lanza Tech is one. There are others. There's heifer. There's power to liquid. So there's a whole range of ways of doing this. And today we really have to explore quite a few of them because we might need two, three, or four of them, just as we need to get the efficiency of the aircraft better. We still need to do that to help this challenge. And we need to add electrification, both for the short haul and there's a supplement to our existing aircraft again as a sort of additional efficiency move. So there's quite a complex picture, but we are all doing all of these things. The good news is everything I've spoken about, people are very seriously looking at how to do. And probably the bit that's still just missing is that making the market bit. But I see a lot of good moves happening there. The EU refuel consultation that's happening now could be a very powerful thing for humanity and for aviation, if that concludes. And governments around the world are starting to follow, hopefully the UK government with Jonathan chatting to them all the time and reminding them of their obligations, which they feel going at hence jet zero. So I think there's a real chance that we're going to do this. And hydrogen may or may not be part of it, but we're not going to shut the door to it, that's for sure. Jonathan and Dick, I'd love to get you in on this conversation because I just heard Dave lay out something that has exciting potential as part of the solution. But as Jonathan, the customer in some way who has to manage these planes in this complex system of where they're going to land and what supplies are there. Dick is a airport where you've got to be able to support any of the planes that want to land and be able to make sure that they actually have the power to take off again. How do you see this as potential or the complexity concerning? Well, I would look at it from the side of the potential and you see it coming back in our own master planning. For example, if you think about the airport 10 or 20 years out, what do you need? So you'll probably need an electric infrastructure in order to be accommodating E-flight. Hydrogen might be the case, might not be the case. So we're certainly starting to factor that in and it's our role to facilitate that. We should not be the bottleneck and I fully agree that we have to shoot a lot of arrows at the moment and explore a lot of pathways. And then at a certain point in time you'll see from efficiency reasons and for economic reasons you'll see what is going to crystallize out and then as an airport we have to be able to facilitate that. But we want to be at the forefront of those developments at Schiphol. So if push comes to shove we will be there. But hydrogen is a very interesting one of course because you see it also in the sustainable aviation fuels part. If you talk about the synthetic fuels you need hydrogen to create the synthetic fuels and there the fact that hydrogen is so multi-usable it probably will be a new vector in the energy system is an advantage as well because you will see combinations. You will see it with industrial or chemical clusters where there will be a need for hydrogen and making sustainable aviation fuels as part of that can be an opportunity as well. And probably for a while we need to settle for hybrid solutions at the same time. There will be a real problem in terms of supply of green hydrogen but there's the potential of blue hydrogen as well indeed made from natural gas but then we see a two capture and storage and that probably won't be the 2070 solution but it will certainly be part of the 2030 and the 2040 solution and we have to take those routes into account as well. I don't think there's any alternative for that because we always underestimate how big the system is. The energy system as such the aviation energy system and how big the investments that we need to make. So we can't be too picky we only want to do this we only want to do that it has to be 100% now because we have to get going. Hi yes and yeah we agree with with the dig there. We think we think that hydrogen has a role to play. I mean when you look at all the roadmaps that are produced for aviation this year that it's quite clear there's no silver bullet. We need everything to be able to get to net zero emissions all all technologies and sustainable aviation fuels and so on. So we believe as has previously been said we think it's a short haul small aircraft short haul but we do have to overcome some of those challenges that have been mentioned around availability of hydrogen competing with other sectors. It's non-drop-ins they have to modify obviously the engines and the fuel supply systems but on the opportunity side we think there's real complementarity with power to liquids because it will enable that supply of hydrogen that enables you to get to power to liquids quicker which we think will be probably the primary sustainable aviation fuel post 2035. So real real complementary complementarity there and also of course they are truly zero carbon there are no CO2 emissions from hydrogen powered aircraft and we believe there are also some potential benefits for non-CO2 emissions which is another issue that we need to address as a sector so we think yeah absolutely potentially it could be a part of the mix. May I make a comment on this? Yes please I want to get Jennifer in and I want to get Jeff in on this conversation so Jennifer please go and then Jeff will turn to you. So we're a big believer in hydrogen becoming an important part of the future of both aviation and liquid fuels as was stated one of the reasons is not just the power to X but also the fact that conversion of waste products the addition of hydrogen in those systems actually increases yield okay if you if you use a waste feedstock whether it be biomass or municipal solid waste often the amount of hydrogen available to convert all the carbon is not there so green hydrogen will play a role in increasing the productivity out of those waste resources the only thing though that I would like to say as as much of a proponent than a potential user of hydrogen as I am I need for us to be very careful I hear a lot of discussions right now about synthetic fuels and power to X and all these things which by the way our technology will work very nicely with but I'm afraid we get way ahead of our skis and so we get bored with things that are working and that is why we have a hard time sometimes replicating because we fall in love with this next big beautiful shiny bobble you know we're going to take carbon directly out of the air we're going to add green hydrogen to that and we're going to convert that to synthetic fuels and we start to focus our energy on these notions and ideas which are great by the way and I believe are the future and then we forget the things that are scaling because scaling is hard that's where the hard work comes in and we just assume look at the next big idea so like I said please do not take this as I'm not a huge believer in fact I spent a lot of time inside my company talking about how we're going to play in the power to X sector but I don't want to forget about the things we can do today that make both environmental sense today and economic sense we have to bend the curve and we cannot bend the curve by thinking about 2030 or 2040 we bend it by thinking about 2021 2022 2023 that would be my my feedback well thank you Jennifer because you're pushed for what we can scale and how fast we can scale is so important for all of us Jeff can I bring you in on here and if you or anyone else wants to talk about liquid hydrogen because as we talk about this I think it would be helpful for sort of everyone watching to to understand the the potential there yeah absolutely thanks thanks for that so we're exploring all of those we're exploring liquid hydrogen gaseous hydrogen all of those I think could be good technologies and our you know our the technology that we're building at right motors and inverters and other underlying parts of the technology the underlying technology that would go into these future airplanes will work with any of those I wanted to pick up on something you said though that you mentioned a few times you said Jonathan Jonathan is the customer the airline is the customer and I think you know that's a really interesting point I think what's interesting about aviation though is that it's it the custom the airline isn't actually always the only customer it can be governments and it's the consumers themselves so going back to the example of California you know the government of California announced that they want all cars to be to be eventually electric the government of Norway has announced that they want all their short flights to be electric there's there's a lot of work that governments and that also organizations like the world economic forum can do to help get the conversation going and shift the narrative so I think you know and especially right now what's going on in in the aerospace world airlines are hamstrung there they have tons of operational challenges they might not always be thinking 10 15 20 years out obviously we want everybody to do that but you know they have day to day work to be done I think the role of the governments and the role of organizations like the world economic forum cannot be overstated and in a sense that's where a lot of this change will happen and so I think you know of course it's got to be collaboration but I just wanted to sort of make that point because I've heard you mentioned it a few times and I think governments and other agencies can also be really have to be part of this this group has had tremendous insight I hate to have to move to close but I think we're going to have to to keep us moving could I ask for closing comments I think we've got probably about 30 seconds per panelist but if you could all give us your your closing wisdom I'd be grateful we can just go go round if someone wants to jump in well I'll kick off I think what we're all saying is we need to make the technology we've got today more efficient we need new technology and we need sustainable aviation fuels and all of those things are possible all are being worked on now and we need to cooperate to do that and we need governments and policy to help drive that and help support that because it's an immense undertaking but it's one we're all really so excited to do as we all become zero knots thank you Dave I find it amazing I find it amazing how how the discussion has evolved if you would have had this panel two years ago it would have been very different in terms of the evaluation of where we are what the options are how to do it and how to bring all the dimensions from technology up until the customers and the commercial site together so I think as an industry we are really evolving but we still have to make a bigger impact in terms of our credibility towards society as well as getting getting the policy piece right. Hi Wendy I'm happy to go next if uh please and I think I think the theme radical collaboration is absolutely the key message for me I mean climate change is not going to be solved by any one company or even one set of companies it has to it's an industry challenge it needs an industry solution so I think and I certainly seem to spend I'd say at least 89% of my time out out of the not talking to within the airline but to other companies so that's at an airline level at an aviation sector level with airports and manufacturers and air traffic control and then with the broader group of stakeholders so we talked about government absolutely key but also corporate customers NGOs academia all those we have to work at all those levels to make this happen and ensure that we can deliver our net zero emissions by 2050 ambition thank you Jennifer sure um the the key comment that would make is that we are often creating false choices of one thing versus another and so the theme of today of collaboration and getting to zero as quickly as possible is really the key we need it all and we need it now no more time for debate no more time for discussion give it a shot if it doesn't work move on but don't overthink it we're overthinking solutions approaches government legislation etc and by overthinking it we're not setting things in motion fast enough and I think we're all watching the world it's on fire right time to act Jeff uh so for everybody out there right now um if you're listening the number one thing you can do to help support sustainable aviation is write your government write your elected officials and tell them you want sustainable aviation and you can play a big role in helping all of this happen so thank you again okay so a huge thank you to our panelists I am hearing the kind of collaboration from this group that we need broadly across the industry and that Charles was calling for at the beginning of this session working across the entire value chain of customers the entire ecosystem and making sure that we deliver the innovation and that those around us can deliver the policy that we need for this to succeed and as Jennifer says at scale quickly so I'm going to hand over to Jane upe so Jane if you could please pick up now I'd be very grateful Jane is the chief of the environmental unit of the international civiation civil aviation organization thank you and good day everyone the current crisis affecting aviation is unprecedented but so is the volume and speed of initiatives for disruptive revolutionary solutions for a greener aviation the pace by which you see the development of electric and hydrogen planes or new processes for generating sustainable aviation fuels it's unparalleled and for the first time sustainably motivated and the international regulations for their certification need to be developed and soon environmental sustainability is also a prerequisite for investment and the flying public wants the ability to fly sustainably long-term commitments are essential for the construct of the carbonization pathways what should not shadow the need to act now iq with its 193 member states is leading and facilitating action now to keep net carbon emissions from international aviation from 2020 at the same level by implementing a basket of measures that includes green technologies sustainable fuels operational improvements and corsia iq global carbon offsetting and reduction scheme for international aviation the first global market-based measure for our sector while our priority is and will remain in sector measures to reduce emissions corsia is a complementary measure to ensure the achievement of carbon neutral growth i'm happy to inform that corsia is on track iq completed all necessary steps for the start of the pilot phase on 1st January 2021 iq is also assessing the feasibility preparing options and a roadmap for a long-term aspirational goal just a few weeks ago nearly 100 initiatives and solutions to reduce in sector aviation emissions were presented at the iq stock taking seminar clearly showcasing that we can dramatically reduce co2 we were inspired by the many examples of zero net co2 emissions for aviation and through by the first hand announcement of the one world alliance commitment for net zero by 2050 the stock taking event is available on the iq tv building upon the momentum created by the stock taking iq is continuing to engage with all stakeholders to facilitate the development and accelerated implementation of these initiatives under the iq coalition for sustainable aviation on that note let me invite you all to the iq aviation green recovery event to be held virtually from 23 to 24 november hope seeing you all there aviators are innovators and as aviation continues to explore most promising innovative solutions for in sector co2 reductions it is imperative that the right policies and legal frameworks the infrastructure needed and access to the fair share of clean energy amongst all activities and sectors are in place with a view to achieving level clean fuel for an inclusive and effective green recovery there is no silver bullet there is no one fits all our measures count and global cooperation has never been so important thank you yeah this is this is christoph wolf i am the head of mobility at the world economic forum as a world economic forum we have put together the clean skies of tomorrow coalition that has been referred to over the panel and i'm thanking everybody to for being with us today let me say a few words at the end to close out i think we i think this was as dick said we would not have had this optimistic panel two years ago so this is great and we learned a couple of things yeah so we learned that we needed all and we need it now echoing what what landslide was saying we do have enough energy on the planet yeah for for for green hydrogen i think we learned that three percent of the sahara will actually supply the energy in the future so we you just need to make it happen in terms for scaling sustainable aviation fuel is is basically a great recipe for scaling because you can blend it you can start with five percent today and you can get it up to a hundred percent and you can even do it with the given infrastructure and electric and hydrogen will play a role but we actually have the technology there today in order to to make it to make it scale now today we actually as a world economic forum with the help of mckinsey and the energy transition commission and rocky mountain institute we are publishing our self analytics report which goes into depth about is there enough feedstock what are the cost curve how can the pathway to net zero 20 20 50 b and we would invite all of you to to read this and we would like to make in the spirit of radical collaboration with our partners from the community i would like to congratulate ikeo for very spirited leadership across the sector i think there's a there's a steady clockwork or the wrong beat of of events and initiatives to um going towards cop i would like i'd like to congratulate also mention our our colleagues from the atek team the aiata that also they just did the waypoint 20 50 and all of this i mean dick was referring to the clockwork maybe not being there but i think this is now i think step after step and the and the basically the reason for this is to build global confidence yeah so we will be in two years um at the ikeo um global assembly and we will we will talk about it will be talked about what the long-term goal should be and i think the the key thing is until then to build confidence that this is doable in a globally equitable way yeah and i told jane if she doesn't say it i will say it nobody left behind yeah so within the within the clean skies of tomorrow coalition so we're looking at finance we're looking at the important role um of the flywheel that that corporates like microsoft can play uh in order to build uh demand early we we work with the eu commission and all the stakeholders on the european green deal and the blending mandate for this to come in early and and scale in a way that it's rapid it can be rapidly but we also we started with india with the basically all 40 stakeholders in india what actually um sustainable aviation fuel and the and the and the and the transition to net zero can actually mean for developing country and because that this is where the growth will be but they can also be suppliers to the world for for sustainable aviation fuel and we will go to other countries in order to build confidence with governments and stakeholders around the world um that this is actually doable in an equitable way i want to thank everybody for great contributions and i think was a great um was a great conversation and um so thank you very much from the world economic forum


Great. Hey guys. Hi. Okay. Should we start? Okay. So, welcome to the engine API discussion call number two. And actually this is the discussion session around engine API number three because we had an extra session during the previous ACD call. So, the agenda, the format of the call is the same, stays the same. So, if you want to ask Stamson or just put a comment, feel free to interrupt me at any point. If we are falling into deep discussion around some particular thing, we will likely break it and follow up on that in the discord in order to not like, like, distract the general line of this call. And also, we have an agenda for today. So we'll start from some small change to the minimal set methods that has been done since the previous discussion session, and then go to the transition process. And I'm not too optimistic that we will reach the end of the document today, but I think we should cover most important parts by the end of this call. Okay, so let's get started with the change to the minimal set of methods. The first one is that it's been discussed on discord, I guess, with Micah and Jim. And I think it makes sense. If engine prepare payload is not like if like building a payload in advance is not supported by a client. It should be implemented as a no op. So it will just do nothing, but the consensus client will will not have to adjust its usual more build and flow dependent on the client on the execution client implementation so it makes a lot of sense. And I think anything to comment here. What is the get payload limitation will now depend on prepare on this support of prepared payload. If it's fully supported then get payload should must return immediately with what has been built, whatever it is, even if it's just the empty payload. Consensus client will have a guarantee that it's response immediate, but if the like prepare payload is not is a no op is not implemented then get payload will work as follows it's just will go to the mempool select transactions from it build the payload and return back so it will go some delay. Also, prepare payload and get payload might be overridden by the like by by clients that are optimized for MEV. And in this case to prepare for the no op and the get payload will if there is the block builders in place, it will just return the fully a full payload to the consensus client. So it will also it should also work like it should also be an immediate return and yeah this is just an opportunity for MEV clients how it could be implemented. So the Micah. So, we can discuss this further in discord I thought we talked about and agreed to and sounds like we must understand each other that get payload would always return immediately. And it's up to the execution engine to, you know, figure out how to do that. If they're running MEV client of some kind that might just be, you know, grab latest block and return it because presumably they've already pre validated those, or if they're not running MEV, then maybe this return empty block or their return block they built previously but I thought that get payload is always supposed to return right away, like as fast as possible. And if you want to do more processing you should do it after you get the prepare. Okay. Okay, I see. So just build the block on the prep a lot and doesn't update it right. This is like the potential implementation, the potential behavior. If it's if the client doesn't support this constant data of the block that is being built. So you even that case like, I guess my assumption is from from like an API design standpoint, it's very beneficial if the, there are strong guarantees that the clients can rely on and timeliness of response to get payload is important because if you have if the client doesn't rely on a very fast response from get payload, then they can wait to the last minute to send it, which is desirable because you want to wait as long as the client feels is reasonable, because you're more likely to get better transactions more expensive block etc. Whereas if the client has to assume that the get payload response may be slow, it means they have to send the get payload request sooner, which means you have less time to build a better block. So I thought, again, we can talk about this more in discord. I think you and I must have misunderstood each other as all. Yeah, yeah, yeah, yeah, I get it. Yeah. And yeah, to agree that. And we specify like a time constraint that we would need to have a response by. The trickiness with the time constraint is that it's highly dependent on your like internet architecture. If you have your consensus and execution client both run on the same machine, then you know the round trip time is less than a millisecond and so you might have, you might be able to wait until kind of even more the last minute versus if you're running distributed maybe across that data centers or cross multiple machines across the world or whatever, then you need to send it much sooner. So I worry about kind of do it a protocol level time constraints there. Just because I feel like it's highly dependent on your architecture, like your constraint is don't use this message to start doing really hard work and instead to final finalize the bundling of a block and pass it along. Isn't, isn't that what prepare payload is. This is in the case for prepare payload wasn't called. So, yes, if it get payload is called essentially like should it at that point try to do hard work or should it just pass what it has which may be not something very good. And I think the implication here is past what it has. It might not be very good, or maybe it uses some sort of pending block structure, and it should just pull from that but it shouldn't be a an initiation to like do work that's going to take a second or three or eight. I think that prepare payload must be called anyway anyway, so it should be like a requirement so that get payload follows the corresponding prepare payload call. Sure, I meant if prepare payload wasn't no often. Oh yes. Okay, I thought you regard this wasn't called. And I have a question for what is the, what is the consensus engine supposed to do between the calls of prepare to prepare payload and get payload. It's supposed to keep listening to the big engine network and probably update the head. In between and the call prepare payload once again with the new head. So it may potentially issue multiple prepare payloads and then only one get payload is that's what you're saying. Right, if another prepare payload, the new primary say, right. Yeah, so it will the process of building a block will be restarted with like. So, so, so what I'm getting it is that the reason why this things has been split into two pieces right into prepare payload and get a payload is that because you might have a multiple of the first and only one of the second right. The initial reason is that the proposer wants to start wants to initiate the building of the payload in some advance. It knows that, like, during the next slot, or the next couple of slots, like the next few slots. It will have to propose a block. And at some point in advance it starts some point prior the slot that it's supposed to propose. And so it has all the information to prepare it but it's not yet the time to do it. But actually, yeah, actually the continuous nature of like proof of work where you're always about to try to, you're always trying to make a block. This is, I actually know I'm going to be proposing a block and call it four seconds. So I signal that the work is done and then I don't have to have this like pending block operation running continuously which apparently is pretty heavy depending on the implementation. Actually, yeah, this random parameter makes it no in this parameter I mean it is like is only known after the parent block has received so upon receiving the parent block it will. Every time the, there's a new head. The prepare payload needs to be called like after in order to start building the block from that head. Right, yes. Yeah, and also if, like the block from the previous slot is delaying. It could arrive later but the proposal might want to. So it seems to me that this reason the real reason why we have it right now not in the original reason is that you wanted to make this operation of preparing parallel interruptible so that you don't have to keep, because obviously you could run it in multiple threads and you know the choose the one that you wanted but you really want to interrupt the previous work to restart the new work. Actually it depends. Yes, I mean yeah, oh yeah we have an option here so we can add to the protocol that there is an option. No because I think it's everything else could be could be simulated with other means I think the I'm trying to understand the real reason why the real reason is that the, when we're speaking with death on a call previously is that there was only to get payload, which is implied that either work needs to be continuously done before, kind of like how pending block is done today, or it needs to be done at that at that call which can take a long time to get something valuable. And now that we know what the proposal knows at least four seconds before proposal maybe eight that they're going to propose and what they're going to build on, they can send that signal. Other than the continuous pending block work being done all the time, they can just signal to do it and get it. There's the exceptional case that you then might want to handle where there's a reorg in that timeframe, which is actually very unlikely. This configuration but you could get say eight seconds before I think this is going to be the head that's going to be built on I know I'm going to be the proposer, I send it. And then four seconds later I actually got a reorg, and I want to override my previous repair payload and then at the time of me proposing I call get payload. The, the motivator is, is the is the prior thing that I've said but then you need to handle the case where reorg happens which is why you might send to prepare payloads. Yeah, right. Just not. Any questions. I have a follow up question, is there any sense if like we get multiple prepay prepare payloads to construct multiple blocks and then one of them would be chosen on gate payload or is like, if we get another we definitely should cancel the previous work is there any like case for that. Yeah, I vote line in the, like section that is in the bottom of the document. Yeah, it might be the case when you're there are multiple consensus clients that are using these that are sharing one execution client, and they are concurrently and wants to build one the payload to be built on top of different parent blocks but that's an exception use case and should not be like. Yeah, I mean that's also implying there's multiple heads, which is not, I think generally how this API is being designed. Yeah, and it will have to support like multiple versions of mental from what I understand. If we want to keep building the payload on top of different and if these two heads are on the same chain right if this is if this is this are the parent and the child blocks so it doesn't make sense to keep building the payload on top of the parent block if you already see that there is a child. Yeah, in case of the child has been delayed and was running late. Just understand that the dependency graph.  Shouldn't it just. I mean would you even need to call prepare payload again or would it. Just have it assume that. Okay actually you need to restart from this new head and the dependency graph is always like to build a block you need a head. Right but you should restart because this random parameter will be changed. It doesn't sound like correct choice updated. The random that's in there is only known by the next proposer is that correct. According to the current spec. Yes. But there is a PR. Yeah, not to mention a fork choice updated might even change the proposal shuffling and so you might not even be building a block anymore at that point. So, I don't think you want the fork choice to automatically interrupt this work. Is there a cancel build then in that case. Yeah, get a payload choice changes. You need to tell the next use engine hey stop building. You're not coming up next can also just know to cancel if certain time stamp has passed. It seems to me that like, you know, one thing I first noticed when I saw the separation is that there is this assumption about some state which is inside of the. So associated state is the kind of this makes it a state for API so when you do the prepare payload, it creates some kind of state that then you later rely on. Now we are coming to the, you know, just suggestion or maybe you should be cancelable. But then, you know, when you call the prepare payload, you implicitly think that the identifier of the state is parent hash plus random. So if somebody else gives the same pair of numbers than they will be referring to the same one. I think maybe it's better to explicitly return some kind of state ID than you can manipulate it doing cancellation or whatever you want to do, because there's there's kind of lots of implicit state here and then it might be that different. It might actually be complicating the discussion. I think it's technically stateless like I definitely see where you're coming from with it being a stateful because you're saying like you anytime you have you know a then be sort of situation. It's generally looks stateful. I'd push back slightly just because the payload actually contains the exact same information set. And so the prepare payload is more of just like a warning that you can choose to heed or not that saying hey, I'm going to be asking for payload later with these exact parameters. Feel free to start working because when I asked for it later I'm going to need it right now. And the excursion client can choose to not do that like it doesn't you technically you could have an execution client that completely ignores prepare payload it is not actually required for the protocol. It's actually required if you want to be able to have time to actually build useful blocks like if you're okay with not building useful blocks. You don't technically need it which is why I think it's it feels like it's not actually stateful just because it's more of just like an advanced warning system. Well it is you essentially not what you said is that the the combination of parent hash random is timestamp in there is that kind of this ID of this stuff which is. This ID it's more just like I'm about it's saying I'm going to in four seconds ish, I'm going to send a request to ask for a thing, and that request is going to ask for these something built the function of these four items. If you didn't get that for some reason, you would still get the follow request and you would still be expected to respond to the follow request just the same. It was just like a headset. Not sure, but you know there's a lots of different those questions if you don't specifically specify what is the ID then you say okay, what if I have one request which has got parent hash and timestamp but another one has the same parent hash but different timestamp. Do I need to keep the first one or replace it. I mean, you know, you know, of course we probably know the answers to all these questions but it would be good to specify what is the actual ID of the of this request, because basically kind of request ID or something. An execution client could definitely implement that by just literally just concatenating those four parameters or hashing them. And that would definitely function as a request ID and I can definitely appreciate an execution client choosing to implement that that way. And so that way you can decide, you know, okay this is the one that's associated with that like internal if your internal architecture that's more amenable, I think that would definitely work, because you will get the exact same parameter set in the get. So I would like to read the prepay a lot call as like in similar way as in the proof of work. The new block has come and become the head and you need to restart the process, which is constantly happening. The process of building the block. If, yeah, if this is turned on, I don't know if it's turned on or if there is an option to turn it on or not. I mean like the gas behaviors. So, any, anything to discuss here. I'm not sure what would cause this but what would, what would cause an execution client or consensus client not to send a payload ahead of time and for where they were just suddenly forced to just call get a load and then if we're requiring that it be immediate. But they just send something empty. I don't think it's expected that that would happen. I think it's just we need to design for in case like you just got a connection up for example and the consensus client had like as soon as your connection came up you're immediately up and so you only got to get says a hypothetical. It's kind of like how blocks are continuously mined and tried to be made better simultaneously and so very likely the logic would follow if you had to do something instantaneous that would be that like initial likely empty block with very little state transition and the hashing completed. Yeah, I agree that given the, that although prepare payload should be expected, and she is the proper way to run this API that give payload should be able to be called in the event of like weirds. I don't see any use case for that. I think it's failed a failure. So you could handle the get payload failure. I don't I think you don't want to handle that failure statefully though. I don't know. I don't see any use case for that. I think it's failed a failure. So you could handle the get payload failure. I don't think you don't want to handle that failure statefully though. I don't agree. There are some sections in this document that covers this kind of failures. Yeah, there is also the message ordering section which is new, which proposes much like just strict message ordering. And discuss it later. So unless somebody wants to say, I think you're a second question. If the execution client fails to fail to respond to get payload in time and you have to propose a block can you just propose a block with an empty execution section like basically like a beacon block as they are now. In this case, consensus client. Like, what does it mean fails to respond in time so it will respond later or what, or not respond at all. If yes posing it doesn't respond and you have a, you know, you have to propose this block. Will the beacon client be able to propose a block with empty execution payload itself. Yeah, theoretically it could be implemented as a fallback and with the time out on get payload response. But the state, does the state root change. If there's zero. No, it should not as we don't have the rewards anymore. I thought, so I thought that this glance could do fill slots without an execution payload and said not correct, or is that changing in the merge that is not. Okay, so there has to be something in that place and that something needs to be valid. You have to still essentially be able to chain something even if that something was empty. So I think that in general, we're designing under the assumption that you can make this request happen. And otherwise, your client, which is the unification these two things failed you and you were able to compute the hash. Okay, so it needs to be a valid block execution block header, at least, like that's the minimum required to fill a slot. Yeah, you could. I think that in general, we're designing under the assumption that you can make this request happen. And otherwise, your client, which is the unification these two things failed you, and you weren't able to produce blood. Yeah, you might be able to design some like logic and that you can chain client to be able to bypass this by hoisting some of the logic into there. But I don't. I wouldn't get on that. I agree with any here so we have a client and is, we have like the composite client and it's just fails to produce a block in this case to propose a block, whatever the reason is. And it should be identified. I mean, yeah, definitely be empty, like the failed proposal will be noticed by the owner and investigation will happen.  Okay, anything else here. Next thing, I've added this confirmed block hash stuff here with the like tentative list of tags for Jason RBC, which will be extended from what we have now and there is the question by Terrence. So, and the proposal to like, for purpose earliest for the big subjectivity checkpoint, which makes sense, but could potentially break some apps, I don't know, or tooling that uses get blocked by another earliest to get the genesis. I don't know if this is really, really pretty in this case and important use case. Yeah, but we can discuss on this later I guess in this court or on the other. This kind of call. Okay. Yeah, also there is like the. There was the block persistent flow now there is the block proposal flow, which covers the like block proposal stuff. Yeah, there is a couple of sequence diagrams. That are the example of how the block proposal flow should happen. So we may take on it and take a look on it and get more understanding, I hope. So, yeah, so any questions to the minimal set of methods before the transition process. The process is also in the minimal methods like set. But it's something new with respect to, to the iranism consensus to see. Okay, so we will start from this one. So terminal total difficulty override. I would rename this to terminal total difficulty updated, because it's not only going to use for override but for also to set the initial value of the terminal total difficulty that is computed by the consensus layer at the merge hard fork, and then it will be updated to the execution client. So it maps on the terminal total difficulty property from the EIP. And yeah, it could be reused further to override the terminal total difficulty with a new value in case if we want to accelerate the merge. The corresponding full request to the consensus by extra repository that adds this possibility and yeah, the like scenario will be the following. The consensus client gets restarted with the terminal total difficulty override parameter, which she will. And this is how the overridden value will be passed to the consensus client and then consensus client upon a startup and connection to the execution client will communicate this overridden value. And the execution client must update this value and act accordingly according to the EIP specification. We should probably state and I think this is probably implied in how this event will be handled in 36.85 but probably say that it's a, you know, it's a no opera can be ignored if the transition has is in process or completed, maybe scope transition implies that. Yeah. Okay, I see. Actually, yeah, we should also add the corresponding event to the EIP, which says that that the terminal difficulty should be updated upon receiving this event and with this event will the new value. Okay, so there is. So let's go through like these two and then stop for questions terminal before block override is the another way to accelerate the merge. In this case, it, it overrides also the total difficulty transition based on the difficulty and direct with specifies the exact terminal proof of work block, and it means that the proposer will need to be started building the proof of block change to build transition block on top of this exact proof of work block. It also implies that the transition client, for example, should must stop processing blocks after this one, it must disable the blog gossip upon receiving this message, and some other stuff which is it which is not yet clear is specified by the EIP, but it will be specified like what once we once we get to this functionality, so it will be updated to the IP. So for this is also minimal set really just the first method is part of that minimal set like to get, you know, implementations going right. Sorry. What do you mean minimal set minimal set like minimal set to be a functional client or minimal set to on like the next wave of dev nets. No, no, it's like minimal required set for, or the other function client. Yeah. Okay, so, yeah, there will be a corresponding printer in the consensus clients that will set this value and communicate and then consistent client communicates to the execution like likewise with the typical stuff. So there be any advantage to using the block height instead of a block hash, you know, you only know the block hash right as it's, as it's been made the when it is blocked because in case of like attacks, they might be multiple blocks at the same height. And we need to specify the exact block. This is an emergency like coordination in which you're picking a hash in the past that you're coordinating on and you're probably taking some chain downtime to do so. Gotcha. And the terminal total difficulty is under, unless under like attack scenarios is superior. And we also you don't do the block height. You do terminal total difficulty because somebody can have like a cheap shadow chain that could reach a block height much faster than main net and try to take over the marriage so terminal difficulty shows and when you're taking something in the future. Yeah. So two questions one, is it expected that the execution clients will have a default terminal total difficulty baked in and they will only receive that message if there is the change or will they always can they depend on always receiving at least one of those messages at some point before it happens. They will receive it. It's not possible to know it in advance. So it will not be hard coded. It's possible but we, we, yeah, we decided to the decision was made to use the computed value. So it will be. So the execution client will always receive at least one of those messages is an accurate the terminal total difficulty override. Right. You mean you mean receive it during one session so at the end of the beginning of every session, it just gets one of those things right. That's the, that's a good question, like session of communication right. Yes, so because then it doesn't make an assumption about whether they stored in a database or they forgot about it or whatever. Right, right, right. So, yeah, it will be computed once but it should be communicated every session as you've said. Yes, I think it could be written in the spec that the consensus client needs to send those at the beginning of every session to make sure that they in sync. Here is the message. Here is the call that's giving it's like this kind of stuff, total difficulty and we will reach this place in the dog. Okay, so you may actually receive that status message but not the override that be accurate. Right, if it's been like. Yeah, yep. Exactly. So the, the override will happen only once when it is already or it's just set initially. So second second question, the for execution clients. Is it easier for any of you to have the block number included in addition to the hash for that terminal proof of work block override, like, when it comes to finding some old block is the hash always enough to never need a block height, like there's no database architectures that make are easier to find the block with height. My intuition is that it's straightforward to request by block hash either from the network or from the storage block has should be fine so something we just block us in the database. Yeah, that's as I wasn't sure if everybody's database has a index by block hash or some of them maybe just actually have like a linked list for example. The block hash we have also separate indexing by number but it's not from number to block but from number to a list of blocks, if you have multiple siblings. But by hush you can find both the main branch and the canonical and non-canical branches so by how she's the fastest way of accessing the books. So, any other questions here. If the session starts with communicating the terminal difficulty. What, like, then the purpose of these two calls is if you is so you don't have to restart a session. But if there's an emergency. Yeah, actually you will have to restart the session if it's the client will be restarted. So what is the purpose of these two calls then like how would it be different. Right, right. One can imagine a consensus client where you could override the terminal difficulty or the terminal proof of work block via an API without a restart. Yeah, I don't know if any of the consensus clients will do that but like from a design standpoint I can see that as being very reasonable. Anyway, it's the consensus client that sends one of these two terminal messages and they also start the session with information about the terminal. I see. So the both of them can change at runtime and one of the terminal difficulty isn't actually known at startup like today, for example, we don't know terminal difficulty. There will be a point in the future where we will learn what that is and it was sometime after the mergers scheduled and so ideally we wouldn't want to have to restart everything just to propagate that new information. Right, this could be sent during the session, and these two will be sent could be sent at the beginning of the session that be sufficient. Okay, but this one should be supported. But it could be supplanted by status message if we will eventually agree on adding the status one. So, moving on to get to work block. Okay, this is actually this has it pulls the same set of data that the get blocked by hash. The only difference here, and this is important is that the execution client should request these block that request by this hash from the wire. If for some reason it hasn't been received from gossip. And, yeah, we might not want to implement this method and instead use the get blocked by hash but imagine the case when the whole the node stuck at the transition because it hasn't received the terminal approval for block wire gossip. I am wondering how likely this could happen. And yeah, if it happens, only a manual restart can help to recover from this case from the situation. So it would be great if we have this one, but I'm open to any opinions on that. So, what exactly is happening with. When, when would this be called. When the transition block is received the transition block is the first proof of stake block in the system. And this method will be used to pull the parent of this block, and the parent of its parents to verify that this is the value terminal for the block. And, yeah, this code is is running in the book choice of the consensus client to accept the block. When you call. So it's, it's, I have a proof of stake block, and I'm concerned whether it actually was built on the terminal total difficulty block, like on a terminal to the view block and I use this to. Yeah, you may use this but it doesn't has this property of making the client to pull the block from the wire if it's missing local storage. So it's basically saying because this client is saying there exists a proof of work block out there that we are very confident exists if you don't have it go figure it out, like do whatever you need to do to get this block. Whereas get get blocked by hash normally it's like, hey, here's a hash. Let me know if you have this block. I want it be more authoritative here because this is the point where the proof state client is, or the client is taking over right and so they're saying you will, you must have this block for me to continue working. Is that accurate. Right. Otherwise we're getting stuck here and they imply that when they run execute payload on the transition block to because execute payload has the parent hash. And it's pretty much saying you must have this parent hash, and if you should go find it otherwise I'm not. I think I'm not understanding what exactly this message is for. Um, you're not executing payload, you're not executing payload during the folk choice. Right. So you're checking that this is the right. This is the right proof of stake block, like the right transition block. So, with respect to the transition process not with respect to the, like, execution yet. So it will be executed later. But at this point you just want to understand before falling into the state transition function. And what is, what is POW block, is that include terminals or with the unit or something. Yeah, let me open it here. So here it is. It has all the required information here is what's going to help me. And here is the code right. So it's before the state transition, and it's important to be before. If, if we get stuck here. So we're not doing the state transition and that's it. So the client wants to know that this is actually a valid terminal group of work block that when it sees the initial transition process and the exists the other methods don't really help us ascertain that. And so there's an exceptional call here on this transition to make sure that somebody didn't create like a bad transition block. Yeah, because it might be a valid transition it might not have picked the right parent block or valid parent block. Okay. I suppose that payload can can do that though for you, because execute payload knows the terminal total difficulty and could tell you if you built off of something invalid, but it might be good to just be explicit here. The execute payload actually doesn't tell about all the difficulty, but we can check it inside of the stage position that is what you mean. I'm saying the execution client knows about terminal total difficulty. And so if you did execute payload and it was the first and execute being built off of a work block it could know if that was not. Oh yeah you you mean we can you we can defer this check to the execution client. Yeah, I'm not convinced that that's correct I just am now understand why this why this exists. Okay. Okay, I want to think about a bit more. I don't think I much more say I'm not. Yeah we have already some implemented we can use this one, but as it's been said, it doesn't go to the wire, if the block has missed. The question to the execution plan mirrors, how often the, you know how often how likely the gossip to be to not deliver your blog or its hash. How often do you do you do your like clients have to go to the wire to pull the parent of some blog that you have received but some reason you've missed the parent blog. Yeah, I agree with Michael, but this is fairly unlikely, but it happens especially on like some network blips etc. So yeah if you say that we are pretty confident that that this method will work. Well, so we will just remove these from the design space. Well, it might not work but we're kind of thinking that the, the, the, the probability of this occurring everywhere it's very small, like it might occur in one or two nodes or something. So it means that if. Yeah, there will be a very little portion of nodes that might get stuck right, even if we even have this kind of notes. If you, if you follow the like execute payload path, I think the input implication is that execution execute payload if it couldn't, if it didn't know the parent would go find it with the network so it might be better to just run that path. Then we will have to get to this check after execute payload right after the state transition. And the execute payload will actually has an additional semantics for the transition period. It will need to go to the wire and pull the block if it's it and pull the parent block if it's not in the local storage. It already, it already has to do that though right in order to validate the current block you need to know what the parent block was, you need to have seen the. Right, right but currently consensus client guarantees that that all previous blocks has been sent to the execution where that that I think actually when you start talking about failure modes and synchronization issues between these two pieces of software that like the what we've previously discussed is, say, say the execution engine fails it gets restarted and it's 10 blocks behind and, and the big change client inserts a block that the execution client can then say no I don't have the parent or it could actually just go to the network and get all the recursively look up those 10 blocks and handle itself. That's not out of the question that yes your side actually does do some self mending when it doesn't have a parent. Yeah, that might work. But if in this case execution client falls into the state sink to pull the state. And the apple headers it might take some time. Which is what we are transition process like it's time critical. I think the parent block from the wire may also take some time but probably it is like. Yeah, but probably it will have to pull like one block and it's parent and supports. Yeah, so I think in, in all happy paths that should already have the parent block, I think the primary unhappy path is when someone act actively is attacking the transition, and they have mined a the first instance block on invalid terminal toad difficulty proof of work block. That's the time where you would maybe get a request to hey execute this block. The client doesn't have it because it's not a valid block and it never accepted such a thing. So we are like roughly agreed that it would be better to rely on to get one hash right and on the blog gossip. I think I'm with Danny I prefer relying on this executing the block later but this might be a good conversation to move over discord since we're out of time. Right, right, right. Okay, the next one is sync. Well, like, great work done by Alex and get them on the nursing proposal. I've outlined like this, this thing status was in this document before but there is the same checkpoint set, which is required by which is, yeah, is one of the required methods here. And the, to make the execution client aware of what is the block header at the big subjectivity point. And consensus client knows that what's the header is because it goes the state of the subjectivity checkpoint and can directly send it to the execution client. This is also the first step of the same process. So it's like initiating the same process. And also might be a might be a clear evidence that the execution client should switch to the proof of stake mode. So, I, yeah, a bit of context on that. The execution clients after the merge. Yeah, after the merge happened. And before any execution clients were updates, the execution clients will start in the work mode by default, as they don't know that transition has already happened. And, yeah, they will go to the network to look for the blog and the PS with the greatest difficulty value and so forth and listen to the blog gossip and other stuff. And, yeah, we'd like the consensus client to inform the execution client if the transition transition has already happened. And this is how it could be done. So, once this checkpoint set mess message send aside from the initiating the same process. The execution client may switch to the proof of stake mode and listen to the consensus clients instead of listening to the blog gossip and doing some other stuff. This has to be sent. This is have to be sent every time the execution client is started. I guess no it's it should be sent only on the fresh client start up when there is no box or state and the local storage. There is already some state. It should not be sent. Checkpoint said, actually, it depends if you're behind the week subjectivity checkpoint that it should be sent again, I guess. No, because you just said that it automatically it starts with a proof of work mode and that sounds. It's in the proof of work mode because it's fresh client and it doesn't know about the transition has happened on the net. Wait, but we are going to put the transition difficulty like into the heart for for proof of work as well right. I want to avoid the situation like imagine post post like post merge someone X someone's exit. Sorry, someone's consensus client accidentally crashes right. The execution client restarts. And now they are in proof of work mode but they don't know it, and that that will automatically use some proof of work chain that's like, not really the theme chain. Right, but that sounds dangerous. Yes. But if they start. Yeah, this like switch, I think it should be persisted by the execution client. So it will just start up in the state mode if it's been informed about it previously, even after it starts. And, and also the proof of work client should, if it ever received and saved the terminal difficulty, it should refuse to ever accept any blocks beyond that right. Right. Yeah, exactly. And also, shouldn't we put the default value for that just in the client as an in the source code so that it doesn't have to like what if someone just keeps running a proof of work line without starting up there be compliant at all. Then once again they could end up in a situation where they keep following the proof of work chain. So I think the default behavior should be to stop like all proof of work lines should ideally just stop working if they aren't connected to consensus client. All other behaviors are going to be extremely dangerous. I thought how do we handle the transition process. Do I thought we didn't know the terminal difficulty until like a week before the merge or something that change. I haven't followed that closely. Yes, so it will be communicated like and we can't hard code it because it right right we won't know until after everybody's deployed their clients. Right. Why can't we just like do it but like with other hard folks who we all agree on one block height, we keep the I mean I thought the end points to set it are for emergency like if you say like, oh we need to change it. But like. Yeah, I'd stop here and let's continue with this discussion on this word, because we have one minute to the next goal. Okay, thanks everyone. See you soon I guess. Bye bye. Thank you. Thank you.