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Alternative Aviation Fuels

September 25, 2025 //
1

Full Circle Moment

The 2009 IATA Biofuels commitment turned out to be a full circle moment. The commitment did not introduce legally binding quotas on members, but instead made a landmark industrywide commitment to pursue sustainable aviation fuels as a core strategy for decarbonization. This included a pledge to achieve carbon-neutral growth from 2020 onwards (no increase in carbon dioxide emissions from a 2005 baseline) and to cut net carbon emissions in half by 2050 compared once again to a 2005 baseline.(73rd IATA Annual Meeting 2010)

The pledge kickstarted global SAF adoption and over 400,000 commercial flights have used SAF since then (World Economic Forum 2022/ GE Aerospace 2022). The 2009 commitment led to 2021’s ‘Fly Net Zero’ initiative, targeting net-zero emissions by 2050.

This piece looks at not just biofuels but other options as well.

Note the smoke pollution coming off this amazing looking Convair 880. Pic Credit Larry Pullen

The Background

Aviation Turbine Fuel (ATF) has the following strengths. The first is the ability to operate  at low ambient temperatures,the second is to have a high calorific value, this is measured by the heat produced by a specific quantity, measured as J/kg (1 Wh/kg = 3600 J/kg). The third is volumetric energy density that is the amount of energy that can be stored within a given volume and is measured as Wh/L and ATF with a volumetric energy density of 35 MJ/L has high density. A flashpoint of 49 degrees centigrade obviously makes it combustible and needs to have safety protocols while being handled. Lastly ATF is cheap to manufacture at approx $1.0 per liter. (Aviation Fuel Wikipedia)

By the mid 2000s aviation was under intense scrutiny for its contribution to global greenhouse gas (GHG) emissions. Aviation was responsible for approx 2-3% of all carbon dioxide emissions, and was projected to grow rapidly. (expected to be over 25% by 2050).

While other forms of transport (road,rail,sea) had multiple forms of green propulsion coming up mainly dominated by electricity. Aviation had yet to see any move in the direction of decarbonizing. While the 2009 Copenhagen Climate Conference emphasized sector specific emission reductions there were other contributory incidents as well.

The 2008 financial crisis led to oil spiking at $147/barrel in July of that year and this only drove the point home to airlines, the need to hedge against fossil fuels. Biofuels did offer a hedge against this dependence, potentially stabilizing costs, Giovanni Bisignani of IATA emphasized that fuel innovation was key or else fuel would account for over 40% of airline costs by 2020 ( Reuters Factbox 2008, multiple sources)

By 2009, airframe and engine manufacturers had validated biofuels performance & safety and Virgin Atlantic flew the first flight with a SAF blend in 2008. Furthermore biofuels did not require any aircraft or engine modifications unlike electricity or hydrogen.

Growing calls from countries & private bodies like ICAO further influenced IATA to work on emissions reductions. Aviation was included by the EU in its emission trading system (ETS, a cap and trade policy that sets a cap on the total GHG emissions from specific industries) and added financial incentives/penalties for decarbonization. The commitment preempted stricter regulations through self regulation and fostered collaborations like the Sustainable Aviation Fuel Users Group that was launched in 2008 and united producers, airlines & NGOs to ensure biofuels met sustainability criteria.

SAF

The roots of the idea of SAF can be traced back to the mid 20th Century with the 1940s Fischer-Tropsch (FT) Synthesis. The process which has its roots back in the 1920s was developed by German scientists Franz Fischer and Hans Tropsch to convert coal or biomass into liquid hydrocarbons, including kerosene like fuels (ATF is kerosene). While originally developed to overcome wartime shortages, FT synthesis laid the foundational work of producing jet fuel from non fossil sources.

The Oil shocks of the 1970s further spurred global interest in developing alternative fuels. In 1974 Brazil started the ProAlcool program which produced bioethanol from sugarcane for road transport vehicles. This program demonstrated the scalability of biofuels and catalysed interest in bio-jet fuels.

The 1997 Kyoto Protocol further heightened global focus on GHG emissions. Aviation, which then contributed about 2% of global carbon dioxide emissions, was growing rapidly with no alternatives to ATF came under scrutiny. Initial studies focussed on adapting ethanol and biodiesel processes,  but jet fuel’s need for high calorific values at low ambient temperatures shifted focus to hydrotreating (process of removing impurities such as sulphur and improving fuel quality) & FT synthesis.

Recognizing that biofuels were the path to decarbonizing, with minimal changes to aircraft & infrastructure, the concept of drop-in fuels gained traction. The SAF concept crystallized in 2005 as the quickest solution and was adopted by IATA in 2009 using 2005 as a baseline.DARPA (Defense Advanced Research Projects Agency) took specific interest in this project.

The newfound synergy between all the stakeholders resulted in the first tangible steps. Honeywell UOP partnered with DARPA to develop the renewable jet fuel process. Boeing collaborated with airlines, fuel producers & research facilities to further explore the practical application of bio jet-fuel.

SAF is produced through multiple refining processes that convert feedstocks into drop-in fuels. These processes or pathways convert diverse raw materials such as waste oils, biomass or captured carbon dioxide into hydrocarbons that mimic fossil based jet fuel while reducing lifecycle GHG emissions by 80%.

HEFA (Hydrotreated Esters & Fatty Acids) uses feedstocks of waste cooking oils & animal fats removes oxygen from triglycerides & fatty acids ( fat the human body stores, remember this is from cooking oil)producing paraffinic hydrocarbons (linked carbon and hydrogen atoms, found in fuels and known for their clean burning, high energy density properties)via hydrogenation.Simply put it is gather the grease, remove the oxygen, make fuel like molecules by adjusting the molecular chains or makes fuel from unwanted oils. This process produces top quality SAF. HEFA competes with bio diesel and has limited feedstock availability. However this is still the dominant process and accounts for 80% of all current SAF production. (companies : Neste)

The FT Synthesis uses biomass such as agricultural & municipal waste as feedstock. The biomass is gasified into syngas (carbon monoxide & hydrogen), then catalytically converted into liquid hydrocarbons, which are then refined into jet fuel. While feedstocks are flexible which translates to potentially high volumes, the high capital costs & energy intensive nature of gasification plants are obstacles to the adoption. While certified in 2009, the FT synthesis process is still niche.

Synthesized iso-Paraffins (SIP) / Direct Sugar to Hydrocarbon (DSHC) uses sugars such as sugarcane or corn syrup as feedstock. Fermentation converts sugars into farnesane, a hydrocarbon, which is then hydroprocessed into jet fuel. While this process produces high density fuel, it is a niche pathway with a limited blend ratio and is expensive to produce. (companies: Amyris)

Alcohol to Jet (ATJ) uses ethanol or isobutanol from biomass as feedstock. Alcohols are dehydrated (water is removed), oligomerized (smaller molecules for more efficient & cleaner burning) & hydroprocessed (refined using hydrogen under heat and pressure)to form jet fuel hydrocarbons. Certified in 2016 this process leverages existing ethanol infrastructure and uses versatile feedstocks, however this process is complex and multi-layered, leading to higher costs. (companies: Gevo, LanzaTech)

Power to Liquid (PtL) / Synthetic Fuels (e-SAF) uses carbon dioxide captured from the air directly  and green hydrogen (from electrolysis using renewable energy) as feedstock. The carbon & hydrogen are combined using FT or methanol synthesis to produce synthetic hydrocarbons which are refined into jetfuel.While this is still an emerging process, it is an extremely niche method & energy intensive,it is reliant on cheap renewable electricity. The RefuelEU is an aviation initiative that requires 1.2% e-SAF by 2030.

There are multiple other emerging pathways such as Hydroprocessed Hydrocarbons (HH-SPK) that use algae oils, this is not scaled as it damages ecosystems. Catalytic Hydrothermolysis (CHJ) that converts oils/fats under high pressure & temperature. Lignocellulosic (plant biomass) pyrolysis is the fast pyrolysis (decomposition through high temperatures) into bio-oil, this is an experimental process that upgrades bio-oil to jet fuel.

HEFA dominates at the moment because of its maturity & cost effectiveness, but PtL & ATJ are growing fast. Current global SAF production is at 2.5 bn liters/year ( IATA , Jun 2025 press release )of the total global ATF requirement of 300 bn liters/year.

Neste is the world’s leading SAF producer with operations in 14 countries. Its strategy is centered around HEFA technology using its patented NEXBTL technology to produce high quality SAF. It has the early mover advantage and has been helped by EU policy ensuring a ready market for its SAF. Neste prioritizes 100% waste and residue materials such as cooking oil and animal fat waste. It avoids food competing crops such as palm oil (phased out in 2020). Neste produces 25% of global SAF with three refineries, supplies over 20 airlines and airports and uses logistics partner skyNRG for blending & distribution.

SAF continues to face challenges such as limited waste oil supply, and it costs between 2-3x(World Economic Forum, “The cost of sustainable aviation fuel: Can the industry clear this key hurdle?” July 2025). that what ATF costs, however global policy shifts ensure this fuel is the quickest off the blocks in the decarbonization race.

Note: Could not avoid the chemical terms, have tried to explain them succinctly 

Hydrogen

Hydrogen has always featured in aviation almost from the beginning. Starting with the early 20th Century when it was used for buoyancy on early airships such as the Zeppelin LZ1 as far back as 1900. Hydrogen is known for its high energy density by weight and is seen as a potential fuel due to its zero carbon emissions.

During the 1930s German engineers conducted turbojet experiments using gaseous hydrogen laying the groundwork for cryogenic (hydrogen needs to be stored at -252.8 degrees C for storage efficiency and maximize payload and range. Cryogenic LH2 tanks, though insulated and complex, enable aircraft to carry sufficient fuel for long flights). Gaseous hydrogen would require impractically large tanks, reducing payload or making the aircraft design unfeasible. This was followed by Sikorsky Aircraft proposing liquid hydrogen as a fuel. By the 1950s liquid hydrogen production was scaled for rocket applications. The USAF’s ‘Project Bee’ began with a Martin B-57B Canberra bomber becoming the World’s first airplane powered by liquid hydrogen. Skunk Works led by Kelly Johnson developed the CL-400 Suntan as a reconnaissance aircraft that ran on P&W’s model 304 hydrogen engines. The project itself was cancelled but advanced liquid hydrogen’s production & tankage for the space program.

Between the 1960s-80s both the US & Soviet Union ran tests on passenger airliners using liquid hydrogen as propulsion. Lockheed looked at 130-140 passenger transports with ranges between 2700 – 9300km and the Soviet Union used a Tu-155 with a Hydrogen fueled engine. Both the programs highlighted storage and boil off challenges.

By the 1980s aerospace research considered hydrogen a clean and promising fuel for long range aircraft because of its high energy content and low emissions. Messerschmitt Bölkow Blohm (MBB) , the company that included the historic Messerschmitt Aircraft Company, was heavily involved in hydrogen research. The company was acquired by Deutsche Aerospace AG (DASA) which in turn would be acquired by Airbus. In November 1989 a major European Colloquium was held in Strasbourg, Germany. The main topic of the Colloquium was the future of supersonic & hypersonic transportation systems, here a paper on hydrogen as a propellant was presented. While MBB was a major player in the hydrogen space in Europe, there were others as well.

By the late 1990s the Hydrogen Cell Era had begun and between 2000-2002 the Airbus led the Cryoplane study which was funded by the European Commission had assessed liquid hydrogen configurations for biz jets and widebody airliners, it emphasized safety and infrastructure transitions.

In April 2008 Boeing’s fuel cell demonstrator , a modified Diamond DA20 eclipse became the first manned aircraft to fly solely on a hydrogen fuel cell (HFC). It was powered by Intelligent Energy’s 24 kW Proton Exchange membrane (PEM) system (the PEM is key to splitting hydrogen molecules, the electrons are stripped and forced into the electrical circuit generating electricity, while protons head to the cathodes)  reaching 1,000 meters altitude at 100 km/h for 20 minutes.

Over the next decade multiple organizations such as The German Aerospace Centre, Boeing, AeroVironment etc would make advances in the field of hydrogen flight endurance, altitude,storage pressure (hydrogen being gaseous needs to be cooled and stored cryogenically to maximize fuel), fuel cell architecture. These advances set the ground for the next decade.

The decade of the 2020s has seen increased activity with Airbus announcing its ZEROe project with four hydrogen (combustion & fuel cell) concepts targeting the aircraft in the 100-200 passenger range. While most of the aircraft are conventional there is a Blended Wing Body being tested as well. Airbus targets 2035 for its first first craft with zero emissions.

ZeroAvia is a British/American Hydrogen aircraft developer. In 2020 they tested a hydrogen powertrain on a retrofitted Piper M-class and completed their first eight minute flight. The testbed crashed in 2021  at Cranfield during a power system test, nobody was hurt.Since then ZeroAvia has procured two Dornier 228 . One flew in 2023 for ten minutes with one of its engines powered by hydrogen electricity. ZeroAvia has partnered with Textron Aviation, the parent of Cessna, to develop a hydrogen powered Cessna Grand Caravan.

Universal Hydrogen is yet another company in the field, converting an ATR72-500 & Bombardier Dash 8-300 to hydrogen using hydrogen conversion kits to be retrofitted to flying aircraft. There are multiple other companies in the field focusing on different types of aircraft.

Over the next 25 years expect to see the commercial viability & scalability of hydrogen fuel established in multiple aircraft segments. Airbus definitely heads the area, but there are developments happening across multiple companies and aircraft types. What is critical are the proving flights of today.

Electric

The biggest challenge that electric aircraft face is their energy density. Current lithium-ion batteries have an energy density of 250 Wh/kg which is below ATFs 12,000 Wh/kg. This clearly limits range (once again range anxiety), furthermore batteries add significant weight while reducing payload capacity. Nonetheless, short taxi services are still very much in the picture.

Joby Aviation plans to launch commercial taxi services in Dubai & Los Angeles. They plan to have electric vertical takeoff & landing (eVTOL) services. In 2023 they delivered their first eVTOL aircraft to Edwards AFB and have flown their S4, a four rotor electric eVTOL vehicle in urban settings such as New York. Interestingly the S4 can also be converted to hydrogen and has flown a record 523 miles in this form! They have a couple of interesting acquisitions. The first is XWing which they acquired in 2024. XWing focuses on autonomous aircraft and in a capacity constrained aircraft, autonomy means extra space to sell. The second is Blade Air Mobility’s ride share business. Blade Air Mobility is an urban air mobility platform.

The biggest hurdle to Electric propulsion is battery density and weight. Density is expected to reach approx 400-500 Wh/kg by 2030, this clearly helps with range.

Electricity is definitely on the cusp of revolutionizing urban air mobility and this is predicted to be a $1 tn market annually by 2040. The next generation of batteries are expected to be in the 500-1000 Wh/kg range and this definitely improves range and enables larger aircraft.

Hybrid electric aircraft such as the Airbus E-Fan X bridge the gap between current technology and full electric systems, offering a path to decarbonize larger aircraft using electricity.

The Future

As of today the aviation industry is midway through its decarbonizing journey. The progress is accelerating as is seen from the advances in the last ten years. SAF has scaled from 0.1% of total ATF in 2020 to approx 0.3% or 2 billion liters.Over 400,000 flights have flown using ATF blended with SAF. By 2030 we can expect to see aircraft using 100% SAF. (Robb Report Apr’23)

Hydrogen is still in its infancy, however flights such as ZeroAvia’s 19 seater demonstrator prove feasibility. With almost a dozen aircraft in development, hydrogen powered aircraft should enter service by 2030. By 2035 we can see hydrogen powering about 15% of short haul flight below 1000 km. (ZeroAvia, McKinsey, Decarbonizing the aviation sector, Jul 2022)

Electric aircraft are on the cusp of revolutionizing VTOLs. Companies such as Joby & Archer aviation are planning commercial services by 2026.With rising battery densities , we expect aircraft applications to only increase from here. By 2050 expect eVTOls to handle 13% of all urban mobility trips rising from 5% in 2030. (Icct2020 Jul 2020)

Together these technologies are plugging critical gaps to meet the 2050 net-zero target. This means reducing aviation emissions from one billion tons per annum in 2025 to near zero. SAF with proper blending will account 65% of this with production reaching 450 billion liters by 2050. Hydrogen will complement approx 20-25% of SAFs targets by powering regional flights of below 2000km. Electric aircraft will dominate the short range (below 500km) with 20% of urban trips & 10% of regional flights covering a total of between 10-15% of total flight segments by 2050.

Collaboration & Continued Innovation is key…

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The Flying Wing Part Two – The Blended Wing Body

September 19, 2025 //
4

The BWB is Born

As J W Dunne was conducting his early flying wing tests, there were  developments happening across the Atlantic in Europe. For the very first time, engineers were thinking of using the insides of the wings. A design philosophy was born.

The JetZero Z4. Pic Source: JetZero Website

The Pioneers

In 1910 Hugo Junkers of Germany patented a cantilever tailless wing design. It was an all metal construction (almost all aircraft until then were fabric and wood construction). Such a design & construction would be without any external wires or braces. Furthermore the wings could be hollow and the space used to house passengers, cargo and fuel. His designs were used by the Germans in WW1 and later in WW2 (he was ousted from his company in 1933 by the Nazis). 

The G-38 of 1929 was a major innovation of his blended wing concept and was for a time the largest landbased aircraft in the World. The passengers were seated in the wings which were 5 feet 7 inches thick at the root. The leading edges of the wings had sculpted windows giving passengers a panoramic view as they flew. There were three 11 seat cabins,in addition to smoking & wash rooms. The wings had a gangway through them that allowed mechanics to work on engines while inflight, a first. There were two operating aircraft and flew through to 1941(both flew until 1936)  before the final one crashed.

The G.38 schematic . Pic Source : Wikipedia

The Mitsubishi Ki-20 was based on the Junkers G-38. Six were built as heavy bombers between 1931-35. During WW2 they saw active combat. These aircraft were considered secret and their existence only made public in 1940.

Nicolas Woyevodsky was a Russian Aerodynamicist who filed a 1911 patent called ‘Aircraft’. Here’s where the patent gets interesting. It was filed in the United States in 1911 and granted in 1921 ( how and why did a Russian file for a patent in the USA and why did it take so long?). Not much else is known about this path breaking scientist other than his name, country of origin and patent.

The patent spoke of a continuous airfoil section integrating the fuselage and wings, what we now call the BWB. The patent further described a triangular shaped body with pterygoid (triangular) aerofoil sections that enclosed the engines and passengers. Such a construction would reduce drag and weight enhancing lift. This was considered revolutionary as most aircraft were biplanes with separate fuselage and wings.

The Westland Dreadnought. Pic Source: Wikipedia

Woyevodsky’s 1921 patent led to wind tunnel tests (probably in Russia & Britain) and validated his theory which led to designer GTR Hill of Westland designing and building the dreadnought. GTR Hill was already experimenting with the Westland Pterodactyl. The Pterodactyl was a revolutionary flying wing and flew through the 1920s & 30s in the hunt for a safer aircraft. The Dreadnought unfortunately crashed on its very first flight. After an initial stable take off and stable flight the Dreadnought stalled at 100 feet altitude and crashed, seriously injuring the pilot. The design was abandoned at the time, however It is recognized and appreciated by history.

The British further tried to pursue the BWB airliner design in the late 1930s & 40s through the Miles M.26 & M.30. The data was useful, however a full scale prototype was never constructed.

The BWF (Blended Wing Fuselage)

The timeline between the 1940s & 1990s is a BWB gap (very similar to the flying wings but longer, aviation development had moved rapidly in the direction of conventional aircraft ),except for the military applications between the 1950s – 1980s when the BWF was used. The A-12 Oxcart and its successor the  SR-71 pioneered the BWF design. The BWF integrates the fuselage and wings in a smooth aerodynamic transition, however the fuselage continues to be a distinct structure. 

The SR-71 schematics. The fuselage chine clearly visible. Pic Source : Wikipedia

Such a design used the fuselage as a lifting body, and the chines around the body contribute between 15-30% of total lift generated. The design used Area ruling and mitigated parasitic & wave drag through smooth transitions.

In the 1970s the Rockwell B-1 introduced variable geometry to the BWF. The wings pivoted on 6 ton hinges which are buried inside a wide fuselage. The BWF of the B-1B contributes approx 15-20% of the total required lift. 

The B-1B Lancer & The Tu-160 Blackjack. Note their similarities. The BWF clearly visible on both. Pic Source: Wikipedia

The Tu-160 which has a very similar design to the B-1 has an even larger BWF. The BWF contributed approx 18-25% of the total lift in supersonic flight.

All the aircraft mentioned had variable geometry inlets of various types (spikes / ramps).

The BWB Evolution

The Generation 1 BWB’s commenced in the 1990s and ran through to the 2010s. They represented the ‘ High Risk High Reward’ approach to BWBs where they envisioned extra large 800 seat BWBs with maximum aerodynamic efficiency. This meant Boundary Layer Ingestion (BLI) of the engines and integrating them inside the airframe. This proved to be difficult to accomplish & certify.

The NASA/McDonnell Douglas Studies were funded by NASA between 1993-96. The studies included wind tunnel tests of tailless BWB concepts at 1-6% scale. Models tested had the centre body contributing between 31-43% of total lift and exhibited between 6-8% fuel savings. 

NASA BWB-17 was tested between 1997-2000. With a 17 foot wingspan, the 6% scale RC model was built by Stanford University for NASA. The model demonstrated low drag and had centrebody lift of between 30-40%. The model proved BWB flight handling with a tailless design. The BWB-17 had stability issues and needed artificial stabilization to correct. The model further highlighted scaling & control issues on larger aircraft.

The BWB-17 by NASA. Pic Source : NASA

Boeing Phantom Works BWB studies ran between 2000-2007. Post the McDonnell Douglas acquisition of 1997, Boeing continued to build on the earlier program that ran between 1993-96. 

Part of the program was to construct the 35 foot wingspan X-48A demonstrator in 2004, however the program was cancelled before construction began. In 2005 a 12 foot wingspan BWB model was constructed to study transonic aerodynamics in a wind tunnel. This model exhibited a 15-20% drag reduction and lift to drag ratio of 20-23. As the project was for 450 seat passenger airliners it highlighted manufacturing complexity & airport compatibility issues.

The Boeing X-48B program ran between 2007-2010. It was a 8.5% scale 21 foot wingspan model that was powered by three jet engines and flew between Mach 0.3-0.7. The centrebody contributed 35% of the lift and had L/D improvements of approx 20% over conventional designs. The X-48B continued to have challenges with yaw handling and full size scaling. Furthermore engine out control and stall characteristics were tested and needed improvement. The aircraft needed artificial stability management.

The X-48B. Pic Source : NASA

The Generation 2 BWBs run from approx 2010 to date. Gen 2 highlights a safety first approach to design and has podded engines mounted above the airframe. The realistic path sacrificed potential efficiencies for safety with the approach. The Gen 2 BWBs also explored different propulsion types.

NASA N2A/B/C BWB concepts ran between 2010-2015. The concept was for a 300-450 passenger aircraft. Conducted in partnership with Boeing the N2A had two podded engines mounted on top of the upper surface of the aircraft. Wind tunnel testing was done to study its aerodynamic and acoustic performance at low speeds. The N2B used BLI and had embedded engines. While the N2B showed improvements over the performance of the N2A, the embedded engines increased manufacturing complexity. The N2C was a supersonic concept. The data gleaned from these concepts was to inform the future aviation industry on future design areas.

The Boeing X-48C first flew in 2012. With a wingspan of 21 feet it was a 8.5% scale of a large transporter. The C was focussed on noise reduction and featured vertical surfaces adjacent to the engines.The Modified X-48B had an extended aft fuselage on which the engines were mounted. It completed its 30th and final flight in 2013.

 

The X-48C. Pic Source : NASA

NASA N3-X Hybrid Wing Body that ran between 2013-2018 is a concept design. NASA tests such concepts through computer simulations and & wind tunnels. The research was on advanced technologies and propulsion. Some of the concepts explored included Turbo Electric Distributed Propulsion where instead of large engines, smaller electric fans distributed propulsion across the aircraft. Another concept explored was the Superconducting Power System, where superconducting technology allows for high power density with minimum energy loss. Others included wingtip generators and liquid hydrogen cooling. 

The N3-X can achieve a 70% reduction in fuel burn, significantly lower emissions and noise levels while maintaining performance at the same time.

The Airbus Maverick began development in 2017. With a wingspan of 10.6 feet and a length of 6.7 feet, the Maverick had two engines to the rear with each having a vertical fin on it. The model explored aerodynamic and technical specifications and results were encouraging .

The Airbus Maverick. Pic Source : Airbus

Airbus has further built on its BWB program by targeting 2035 as the first year for a zero emission aircraft. Such an aircraft would use hydrogen combustion or cells for propulsion. Storing Hydrogen is a big challenge in aviation and the BWB is considered an excellent test design. Airbus is further  studying conventional aircraft for its zero emission program. 

JetZero 

JetZero is founded by Mark Page a BWB pioneer. He was part of the seminal NASA / McDonnell Douglas collaboration on the BWB program as technical program manager. NASA concieved the program as a challenge to rethink aircraft design for greater efficiency. The program (although Mark was not part of it after 1996) culminated in the BWB-17(spoken of earlier) the very first BWB of the modern era. It was inspired By Northrop’s flying wings of the 1940s but was a completely fresh approach to aircraft design. The BWB design was co-created with Robert Liebeck & Blaine Rawdon and offered 20-30% better L/D ratios than conventional aircraft. The three of them authored ‘Beyond Tube and Wing’ in 2020 in which they charted the path to the BWB design.

The philosophy was Multidiciplanry Optimization (MDO) integrationg aerodynamics, engines, stability and internal structures to minimize drag and maximize efficiency. Page virewed the BWB as the fundamental reimagining of an aircraft blending wing and body into a seamless flowing structure. In one presentation Page mentioned imagine a Boeing 777 fuselage cut up into three parts and placed side by side. You then stick wings on the first and last sections, the middle one being the longest (with the cockpit) and place the engines on top of the stacked side by side fuselage, and lastly smooth them all together into one fused structure.

Page’s contributions influenced the X-48B/C programs as well. These programs validated the theory of BWBs with subscale models and wind tunnel testing. They sorted out  issues such as space by moving the main landing gear to the rear of the aircraft from the centre, saving space and increasing passenger numbers another example is sorting out pitch stability control issues with belly flaps, every thought had to be out of the box.

Later in 2012 Page co-founded DZYNE Technologies as chief scientist & VP and here he continued to focus on aircraft with high lifting efficiency , but the BWB bug was always there, first as a business jet and later as an airliner. In 2021 Page along with Tom O’Leary founded JetZero to take forward the BWB vision.

Page has mentioned that startups like JetZero are ideally placed to revolutionize the aircraft manufacturing space as they do not have massive legacy businesses that need to transition ex : Boeing & Airbus.

So far it has walked the talk with Alaska & United Airlines investing in JetZero through their investment arms. Delta Airlines is a strategic partner sharing expertize from a customer engagement perspective. In addition JetZero are talking to 14 other airlines and the USAF has awarded a $235 million contract to JetZero to build a full scale demonstrator, but we are getting ahead of ourselves.

The 12.5% scale JetZero pathfinder with its 21 foot wingspan first flew in 2023 and received FAA clearance in 2024. The USAF found the Pathfinder to exhibit similar characteristics to the X-48 program and has given the go ahead to JetZero to create a full scale demonstrator which is to be ready by the first quarter of 2027. The demonstrator is being constructed by Scaled Composites founded by the legendary Burt Rutan who has aircraft/spacecraft such as Spaceship One (won the Ansari X Prize) and Stratolaunch to his credit. Scaled Composites is now part of Northrop Grumman (its amazing the name Northrop is involved here, a doff of the hat to Jack Northrop).

The Z4 is a multirole platform and can be used for both passengers & military applications such as a sky tanker (the USAF is looking at the KC-Z4 as a replacement to its aging KC-135 tanker). To cut down the development & certification runway JetZero will be using Commercial off the shelf (COTS) parts where possible. 

The KC-Z4. Pic Source : JetZero Website

The engine choice is Pratt & Whitney PW2040 each generating approx 43,000 pounds of thrust. These are the very engines that powered the Boeing 757 & the Boeing C-17 Globemaster. While the design of the engines might be almost 50 years old, they are tried and tested and have a solid track record. Delta have provided three engines for the demonstrator. These engines are more than capable of managing the Z4s 5,000 nm range and cruise altitude of 45,000 feet. They will obviously be modernized for the production models. In future the Z4 might be offered with newer engines. Mark Page did note they were not looking for perfect tech, but are more interested in proving the airframe.

The JetZero Z4. Pic Source : JetZero Website

The fuselage ( after the demonstrator)will be made of composites and be manufactured at their Greensboro facility. Some of the other innovations it will have are shorter landing gear to enhance low speed handling, cargo door matching the KC-10 size (USAF applications). The passenger experience stresses comfort & efficiency (the 3D renderings on the JetZero website look stunning).

The personal passenger experience aims to revolutionized by offering larger seats, flexible cabin layout and dedicated overhead bin space (have forgotten what this feels like!). Instead of physical windows JetZero plans on high definition exterior cameras that provide a live view on digital windows. There is a possibility of overhead windows as well in addition to mood lighting.

While the overall exterior design of the aircraft is very sculpted, Page and his colleagues came up with a ‘ T ‘ shaped plug solution to scaling up the aircraft to either smaller or larger capacities, this means the aircraft construction has to be modular in nature almost like ‘LEGO’ !! They did this back in the 90s and the 25 year limit on the patent has expired, in Page’s own words “ I am happy to have it back” !

Page giving a DZYNE Technologies presentation in 2018 where describes the T shaped plugs that sum up the scalability of the BWB. Note their similarities plugs next to the engines. Pic Source : Page presentation off YT

Mark Page emphasizes pragmitism over perfection and this is achieved by delivering on the USAF contract, using milestones to attact fresh funding (the Z4 is expected to cost approx $5-7bn to develop as per Jon Ostrower of TAC) and target the largest market segment for aircraft the 200-250 passenger aircraft market worth over $2.5 Bn per annum. With projected savings of 50%, this will be a no-brainer for airlines future fleet decision making.

BWBs have promises to keep…..

Please be sure to read Part 1 of the two part series which details the evolution of the flying wing in detail at http://theaviationevangelist.com/2025/09/13/the-evolution-of-the-flying-wing-part-one/

End of Part 2

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