Frequently Asked Questions

CAAFI - Frequently Asked Questions

What is CAAFI?
CAAFI is an acronym for the Commercial Aviation Alternative Fuels Initiative. CAAFI is a coalition of aviation stakeholders who are interested in bringing commercially viable, sustainable, alternative jet fuels to the marketplace. CAAFI is engaged in various activities to enable and facilitate the near term development and commercialization of such fuels.

Who are CAAFI's stakeholders (sponsors and participants)?
CAAFI is co-sponsored by the Aerospace Industries Association (AIA), Airports Council International - North America (ACI-NA), the Airlines for America (A4A) and the Federal Aviation Administration (FAA). In addition, CAAFI membership consists of approximately 450 organizations and 800 stakeholders. These include members of other U.S. and non-U.S. government agencies and trade associations, as well as energy producers, university faculty, nongovernmental organizations and consultants.

Why and how was CAAFI formed?
CAAFI was formed in 2006 in response to three concerns regarding aviation fuels: 1) supply security, 2) affordability and price stability, and 3) environmental impacts. These concerns prompted the FAA Office of Environment and Energy R&D Advisory Board to request action on aviation alternative fuels from the FAA Office of Environment and Energy. Following initial presentations by the manufacturing sector and the U.S. Air Force at a Transportation Research Board (TRB) forum in January 2006, FAA, A4A, and AIA elected to form a coalition of interested parties to foster alternative jet fuel development, later formalized as CAAFI; ACI-NA joined shortly thereafter.

How does CAAFI function?
CAAFI functions in several ways. It serves a primary role as a clearinghouse, facilitating the exchange of information about, and coordination of, private-sector and governmental initiatives supporting the development and commercialization of “drop-in” alternative aviation fuels (i.e., fuels that can directly supplement or replace petroleum-derived jet fuels). CAAFI members execute on in-kind work programs, while CAAFI sponsors (and their members) and other public-private partners provide resources for the execution of various work elements. CAAFI often serves as an industry voice that communicates progress and the need for the execution of a very broad range of efforts by the entire jet-powered aviation enterprise.

What is the long-term goal of CAAFI?
CAAFI aims to facilitate the development and deployment of alternative jet fuels that will significantly reduce emissions associated with aviation operations in commercially meaningful quantities while improving price stability and supply security. The availability of fuels produced from renewable feedstocks and/or other waste-streams will help operators reduce aviation's net carbon footprint, even as aviation activity increases.

What does CAAFI believe are the prospects for alternative aviation fuels?
CAAFI is confident that sustainable alternative jet fuel derived from several feedstocks will be commercially available in the next one to five years and is working with other stakeholders to enable various industry goals (FAA's articulated goal of having one billion gallons of alternative jet fuel in use in the US in 2018; the commitment of the commercial airlines and States to achieve net carbon neutral growth in international aviation from 2020 onward, etc.). The types and volumes of alternatives reaching the marketplace will depend on many factors, including the extent of governmental support (R&D and policy), new technological developments, and investor interest. CAAFI is both feedstock- and technology-neutral; that is, it does not support specific technologies or feedstocks to the exclusion of others, but rather seeks to facilitate conditions in which alternative fuels can thrive and compete openly within the bounds set by policymakers and the marketplace.

How is CAAFI organized?
CAAFI has an Executive Director who acts as an overall coordinator and instigator for the work of CAAFI. The Executive Director is supported in his execution of CAAFI work programs by an Executive Director Emeritus and a Leadership Team, which includes a Head Advisor for Strategy and Implementation (FAA) and a Head Advisor for Research & Technical (Volpe) and other support team members.

  • Membership: CAAFI is ultimately a cooperative initiative…a public private partnership comprised of individuals and/or entities who are interested in supporting and/or engaging in the work of CAAFI. There is no cost to becoming a CAAFI member.
  • CAAFI Work Teams: The Work Teams are led by volunteers from the CAAFI membership who are approved by the Sponsors and Executive Director. At present, there are four Work Teams: Research and Development, Certification/Qualification, Environment, and Business.
  • The CAAFI Steering Group (SG) guides CAAFI's overall strategy and efforts. The Steering Group is comprised of the Executive Director and Leadership Team, Sponsor representatives, and leaders of the various CAAFI Work Teams.
  • CAAFI's Sponsors include:
    • Federal Aviation Administration (FAA), Office of Environment and Energy
    • Airlines for America (A4A)
    • Aerospace Industries Association (AIA)
    • Airports Council International - North America (ACI-NA)

What has CAAFI accomplished to date?

  • Fuel Specification Approvals. The CAAFI certification and qualification team works within established processes to help move promising alternative aviation fuels through industry evaluation to approval by ASTM International and other recognized certifying bodies. Government agencies, fuel manufacturers, aircraft and engine manufacturers, and airlines are stakeholders in CAAFI, and many participate on the certification team. The industry has agreed that these alternative fuels should “drop-in” to commercial engines, pipelines, fuel farms, and all other distribution and storage channels, thus requiring no new equipment or infrastructure. With assistance from the CAAFI Certification and Qualification Team, three drop-in alternative jet fuels have already been certified for commercial use (more detail below).
  • Fuel & Feedstock Readiness Tools. CAAFI has developed a collection of tools that facilitate assessment and advancement of fuel and feedstock readiness with respect to ASTM approval, R&D and deployment activities, environmental sustainability, and commercialization. See the Fuel Readiness Tools page.
  • Stakeholder coordination and communication. CAAFI enhances communication among government agencies, aviation sector trade associations, industry, fuel producers, feedstock producers, academic researchers, and non-governmental organizations via the CAAFI Biennial General Meeting and team meetings, Global Exchange with other public-private partnerships around the globe, webinars, conference presentations, and other venues.
  • Strategic thought leadership. CAAFI participates domestically with interagency working groups and strategic initiatives (e.g., Federal Alternative Jet Fuel Strategy, Biomass Research and Development Board, Billion Ton Bioeconomy), collaborative forums, alternative jet fuel research consortia (e.g., Aviation Sustainability Center (ASCENT)).
  • State Initiatives. CAAFI has facilitated formation of supply chains for alternative jet fuel deployment through the State Initiatives, now underway in 8 states within the U.S.
  • Awards and Recognition. Multiple representatives in the 2014, 2013, 2012, 2011 & 2010 Top 100 People in the Bioeconomy (Biofuels Digest), 2011 Washington DC Chapter of Advancing Women in Transportation Innovative Solutions Award, 2011 Washington Airports Task Force Williams Trophy, 2010 Presidential Early Career Award for Scientists and Engineers, 2010 Air Transport World Award

How does CAAFI interact with the other global alternative aviation fuel coalitions?
CAAFI collaborates with alternative aviation coalitions across the globe, including formal work plan development with its Australian and German counterparts, AISAF and aireg, respectively. CAAFI initiated an ongoing “global exchange” of ideas to facilitate complementary work programs and help aviation present a united framework to facilitate development and deployment of advanced alternative jet fuels. The various organizations working to advance alternative jet fuels understand that fuel production and commercialization will be an effort requiring support from various stakeholders and entities.

What is the focus of current CAAFI activity?
CAAFI supports the development and deployment of sustainable alternative jet fuels for use by the commercial aviation community via the following objectives.

  1. Advocacy & Communication: Promote the development and use of sustainable alternative jet fuels by clearly articulating the drivers for the use of alternative jet fuel.
  2. Building Frameworks & Sharing Best Practices: Enable knowledge sharing and facilitate communication, evaluation, and collaboration amongst interested parties.
  3. Coalition Building:Continuously seek to strengthen the stakeholder coalition.
  4. Deployment Support: Foster the commercial alternative jet fuel supply by supporting domestic state and regional deployment initiatives and advising international deployment initiatives.
  5. Engagement & Coordination: Convene stakeholders and enable engagement and coordination on alternative jet fuel activities by facilitating opportunities for connection and cooperation amongst members, sharing best practices, and leveraging success models.
  6. Fuel Qualification: Advance fuels qualification by facilitating communication of stakeholders; establishing a roadmap of qualification activities, plans and needs; providing support for production, testing and approval of multiple pathways at ASTM; and striving to improve the entire qualification and certification process.

When should we expect to see alternative fuels in commercial production?
In the U.S., CAAFI hopes to see production commence in 2015 from the first dedicated middle distillate facility. We then expect the three Defense Production Act (DPA) awardees to start producing alternative jet fuel in 2016/2017. Three alternative aviation fuel pathways have already been approved for use in commercial aviation, and seven additional advanced fuel pathways are undergoing evaluation for ASTM qualification and are likely to come online in the next few years as production capacity challenges are addressed.

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Jet Fuel - Frequently Asked Questions

What is jet fuel?
Conventional jet fuel is a blend of hydrocarbons (molecules comprised of chains of hydrogen and carbon) that is produced from the distillation and refinement of petroleum. This product stream coming out of the refinery is often referred to as a “middle distillate” fuel (between the streams produced for gasoline and diesel) or more specifically, kerosene-type jet fuel. The hydrocarbon molecules are typically in the C7 to C18 range, and consist of three general molecular forms: paraffins, cyclo-paraffins, and aromatics. Each type of molecule has unique attributes, but when blended together they deliver the characteristics needed and required for safe and efficient use in a turbine engine. Other compounds may also added to jet fuel (usually in very small amounts) to improve its overall suitability for aircraft use, including additives such as antioxidants, metal deactivators, electrical conductivity additives, static inhibitors, icing inhibitor, corrosion inhibitors, biocides, lubricity enhancers, and thermal stability improvers. The jet fuel specifications used by the industry do not prescribe the exact composition or production methodologies to be used to make the fuel, but rather simply define the final physical properties that the fuel must exhibit.

What are the jet fuel types?
Jet fuel carries several common commercial and military names, including Jet A, Jet A-1, Jet B, JP-5, JP-8, TS-1, or ATF (aviation turbine fuel). These fuels differ slightly in a few discrete properties, for instance in minimum freeze point, or maximum flash point. Commercially, Jet A is used primarily in the United States, while Jet A-1 is primarily used outside the United States. Jet B is considered an alternative to Jet A-1 in cases of extremely cold climates but not often supplied because it holds a higher flammability than Jet A-1. However, all of these fuels have detailed specifications that must be met, and these are defined by international bodies, the most common of which are ASTM D1655, DEF STAN 91-91. These specifications define physical properties and performance characteristics that the fuels must exhibit. Physical properties (e.g. D1655 Table 1 Properties) include such things as: acidity, maximum aromatics, volatility, flash point, density, and energy content. Performance characteristics (e.g. D1655 Table X1 Properties) include such things combustion characteristics and atomization. Additives are also controlled (e.g. D1655 Table 2), usually by min or max volume requirements.

How is jet fuel used on an aircraft?
The jet fuel loaded onto an aircraft constitutes a large fraction of the overall takeoff weight of the aircraft, and aircraft are less efficient at heavier weights, so the industry attempts to keep the amount of required fuel or energy onboard to a minimum. Because weight is a key consideration, fuel also serves several functions onboard the aircraft, other than just a chemical source of energy, including as a heat transfer medium, a hydraulic fluid, a lubricant, a ballast medium, a conductivity agent, a swelling agent for seals, etc. Then, the fuel is injected as a continuous, atomized stream into a combustor where it mixes with air while burning to deliver a stream of hot, energetic gas to a turbine. The turbine converts the gas energy to mechanical energy (a rotating fan), producing power for the aircraft. As a result of the above, the aircraft system manufacturers are very concerned over the properties of jet fuel.

How much energy is in jet fuel?
For commercial applications, ASTM D1655 requires jet fuel to produce a minimum amount of energy of 42.8 MJ/kg, with densities between 775-840 kg/m3 (or 18,400 BTU/lbm, with densities of 6.47-7.01 lb/usg).

What are the products of jet fuel combustion?
Similar to any pure hydrocarbon fuel, when pure jet fuel is burned under ideal conditions (with pure oxygen), its combustion by-products are carbon dioxide and water. In real world applications (less than ideal, and in the presence of air, which contains nitrogen) the combustion may also result in the trace release of carbon monoxide, unburned hydrocarbons (in gas and particulate form), oxides of nitrogen, and oxides of sulfur (as a direct function of how much sulfur is in the fuel). Regulations exist that limit the amount of pollutants that can be produced. Jet fuel combustion produces ~3.16 pounds of CO2 per pound of fuel burned.

What makes jet fuel different from automotive fuel?
Automotive fuels for spark and compression ignition engines typically include gasoline (and/or alcohols) and diesel fuel. These fuels contain shorter and longer carbon chain lengths respectively, than jet fuel. The shorter chain lengths typically result in higher volatility, and the longer chain lengths typically result in a higher freeze point, amongst other physical and performance-based property changes, making both types unsuitable for aviation use. Automotive fuels are produced to their own unique specifications. Jet fuel is generally produced to tighter specifications than gasoline or diesel (e.g. to guarantee operability, eliminate contaminants, etc.).

How much jet fuel is consumed in the U.S.?
Civil and military aviation uploaded in excess of 23 billion gallons of jet fuel in 2014.

How much jet fuel is consumed in the world?
Various sources estimate that the worldwide consumption of jet fuel is approaching 80 billion gallons per year.

Who produces jet fuel, and how?
Most of the large international petroleum producers/refiners produce jet fuel from their standard refinery operations, as do a significant group of regional producers. Crude oil is converted into conventional jet fuel through several processes. First, the oil is heated then distilled to separate raw feedstock into different output streams based on boiling point. While in separate streams, impurities are removed (e.g. acids, sulfur, etc.) after which the streams are blended to ratios to achieve the specific composition of the desired jet fuel type (e.g. Jet A). Finally, certain additives are installed to improve fuel performance and stability to meet the final specifications.

How does jet fuel get transported to the airport?
Typically, large commercial airports have jet fuel delivered by pipeline to a “fuel farm” adjacent to the airport. But jet fuel is also delivered by rail, road (tanker trucks), and water (tankers and barges).

Can commercial aircraft burn fuels other than jet fuel?
Commercial aircraft can only use fuel that is approved for use in the engine and aircraft operating manuals, as only this type fuel is proven to enable the performance and operability guaranteed by the certification of the aircraft. All of the major engine and aircraft manufacturers require usage of fuel which meets the requirements of ASTM D1655 (at a minimum).

What other fuels could work for aviation?
At present, based on today's certifications, no other fuel types, other than jet fuel, satisfy the needs of the jet powered aviation enterprise. It is not an issue of the turbine not physically being able to burn the fuel, but rather that the overall safety and performance of the aviation system cannot be matched by other fuels. Gas turbine engines are regularly used to power ships and provide power for other heavy machinery or power production, and do so using a wide range of fuels, from hydrogen to heavy oils. But use of such fuels cannot today deliver the same level of performance, safety, and cost as jet fuel for aircraft. Going forward, aircraft producers are investigating a wide range of fuel and energy systems to power aircraft, but none of those systems have proven feasible, or appear to be feasible for several more decades. Significant progress is being made on small general-aviation aircraft operating on hybrid or electric propulsion using fuel cells and/or batteries, but such systems still appear to be an order of magnitude off in key performance attributes of delivering sufficient kJ/kg or $/kJ to be reasonable for commercial aircraft. As such, the jet-powered aviation enterprise expects to continue the use of jet fuel through the middle of this century.

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Alternative Jet Fuel - Frequently Asked Questions

What do we mean by the term alternative jet fuel?
Generally, the aviation industry means jet fuel derived from a source other than petroleum. Specifically, CAAFI and the Alternative Jet Fuel community means a fuel produced to the requirements of ASTM D7566. It can include drop-in jet fuels produced from a broad range of hydrocarbon sources (feedstocks) using a wide range of conversion processes. We sometimes refer to these fuels as synthetic fuels too—fuel produced from sources other than petroleum via biochemical or thermochemical processes.

What is the difference between an alternative fuel and an alternative jet fuel?
An alternative fuel could be any generic fuel derived from a source other than petroleum. It could include compressed natural gas, liquefied natural gas, hydrogen, alcohols, biodiesel, etc. However, none of these fuels are suitable for jet powered aviation, either current models, or those in development, for various reasons discussed above. The aviation community needs jet fuel for safe and efficient operation, whether that is produced from petroleum, or sources other than petroleum.

How long have commercial aviation entities been pursuing alternative jet fuels?
Alternative aviation fuels activity had been developing slowly since the 1970s, largely through the efforts of the U.S. Air Force and a group of engine companies. When CAAFI formed in 2006, the ASTM committee had begun the process of streamlining their certification processes for alternative jet fuels. A blend of synthetic and conventional jet fuel produced by the South African producer Sasol was approved by ASTM and began being used on flights in and out of Johannesburg in 1999. In 2009, approval of the new ASTM D7566 specification for synthetic aviation fuels, with the ability to add annexes to it for new alternatives, once proven, heralded the true dawn of the era of alternative aviation fuels.

What is a drop-in alternative jet fuel?
Drop-in alternative jet fuels are completely compatible with a conventional (typically petroleum-derived) jet fuel in terms of materials, safety, and composition. A drop-in fuel does not require adaptation of the fuel distribution network or the engine fuel systems, it can be used “as is” in vehicles and engines that have historically operated with only conventional fuel. Some alternative jet fuel blending components may become “drop-in” only after being blended with a conventional fuel to a certain prescribed proportion. Currently, approved drop-in fuels only supplement petroleum-sourced jet fuels in blends up to 50% (FT-SPK and HEFA-SPK fuels) or 10% (SIP-SPK fuels). Certain alternative jet fuel concepts do have the potential to be used without blending, but have yet to be approved. Drop-in fuels align with CAAFI's goal of bringing sustainable alternative jet fuels to market.

What are key challenges relating to alternative jet fuel development and deployment?
General challenges include feedstock availability, required life cycle analysis (LCA) evaluations, understanding the fuel chemistry of alternative fuels, cost competitiveness, commercial production capacity, and competition among other bio-based products, to name a few. The CAAFI R&D Team has developed a series of white papers addressing the key challenges related to alternative jet fuel development.

How do alternative aviation fuels perform with respect to life cycle greenhouse gas (GHG) emissions?
Depending on the feedstock and production pathway used, alternative aviation fuels may offer reductions in GHG emissions when compared to conventional fuels. For example, research suggests that hydroprocessed esters and fatty acids (HEFA) from palm or soy oil can have as little as half the emissions of conventional Jet A, assuming no land-use change (see Stratton et al. PARTNER report). However, land-use change can be critical with any biomass, as converting tropical or peatland rainforest to biomass production can increase the life cycle emissions by several orders of magnitude over that of traditional Jet A. More about land use change can be found on the EPA webpage on Sources of Greenhouse Gas Emissions. CAAFI and the aviation community are committed to carbon neutral growth starting in 2020 and therefore are interested in alternative jet fuels that have GHG reductions compared to standard petroleum-based jet fuels.

How do alternative jet fuels perform with respect to local air quality pollutant emissions?
Synthetic fuels afford the opportunity to lower local air pollutant emissions through the reduction of sulfur and aromatic compounds. Thus, when blended with traditional fuel, overall sulfur and aromatic content is reduced. Research also suggests that some alternative fuels may produce less particulate matter (a growing concern for local air quality).

Do alternative jet fuels affect aircraft performance?
Effects can be slightly positive and negative, but overall operability and safety are maintained. For example, lower density fuels can improve fuel burn, but adversely affect an aircraft's maximum payload-range. CAAFI and the airlines are exploring all performance impacts.

How will alternative fuels affect airports?
Benefits to airports are possible with alternative fuels. To the extent that airlines have access to environmentally beneficial alternative jet fuels for aircraft, the emissions associated with airline flights may be reduced on a life cycle basis. Airports that own and operate ground service equipment can also see environmental improvements in the operation of their own equipment, as alternatives for such equipment can reduce greenhouse gas and local emissions as well. A handbook to evaluate costs and benefits at airports is under development via Project 02-07 of the Airport Cooperative Research Program (ACRP).

How are feedstocks converted into alternative jet fuel?
The industry has determined that there are several ways to convert the carbon or hydrocarbon content of various sources into the chemical components of jet fuel. These can include biological process (fermentation or microbial conversion), or thermochemical processes (gasification, torrefaction, pyrolysis, catalytic conversion, hydroprocessing, etc.).

Before aircraft can use any alternative jet fuels, those fuels must meet rigorous criteria spelled out in aviation fuel specifications, both physical properties and fit-for-purpose properties. The specifications for alternative jet fuels are defined in ASTM Standard D7566, and specific annexes to the Standard apply to individual processes for producing alternative jet fuel.

What alternative jet fuels can be used today? (more on the ASTM Approval page)
The three approved alternative jet fuel types represent three different processes associated with three different feedstock types: Fischer-Tropsch Synthetic Paraffinic Kerosene (FT-SPK) which converts syngas (from biologic or petrochemical sources) to jet fuel components; Hydroprocessed Esters and Fatty Acids (HEFA-SPK) from plant and animal oils; and Hydroprocessed Fermented Sugar-Synthetic Isoparaffins (HFS-SIP) made by microbial conversion of sugars to hydrocarbons.

  • For FT-SPK, a carbonaceous source (biomass like forestry products, grasses, or MSW) is gasified at high temperatures (1200-1600˚° C) into carbon monoxide and hydrogen primarily, and the gas is then converted to long carbon chain waxes through the Fischer-Tropsch (FT) Synthesis. The wax is then cracked and isomerized to produce drop-in liquid fuels essentially identical to the paraffins in petroleum based jet fuel.
  • In HEFA-SPK, natural oils are converted from lipids to hydrocarbons by treating the oil with hydrogen to remove oxygen and other less desirable molecules. The hydrocarbons are cracked and isomerized, creating a synthetic jet fuel blending component.
  • HFS-SIP entails the fermentation of sugar into a hydrocarbon molecule using modified yeasts. The existing approved process produces a C15 hydrocarbon molecules called farnesane, which after hydroprocessing to farnesane, can be used as a blendstock in jet fuel.

What is the process for jet fuel development and approval?
CAAFI has developed guidance on getting an alternative jet fuel approved by ASTM, and participated in the creation of ASTM D4054 which outlines the process for producers. Before the process of jet fuel approval begins, it is first important to evaluate whether the fuel encompasses three major factors: appropriate composition, material compatibility, and fungibility. The first suggested step is familiarizing your company with the aviation community. The next step is to perform a technical and environmental evaluation of the fuel in several critical areas to determine the environmental benefit and viability as a fuel for aviation. The third step in the process is receiving fuel approval. Finally, once approval is reached, networking to initialize collaboration with appropriate stakeholders (e.g. feedstock producers) and purchasers (e.g. airlines) for commercial production must be undertaken. For an extensive overview on jet fuel development and approval as well as links to helpful resources, see the CAAFI Path to Alternative Jet Fuel Readiness document here.

When were these alternative jet fuels approved for use?

  • Fischer-Tropsch Synthetic Paraffinic Kerosene (FT-SPK). Synthetic fuels derived from the Fischer-Tropsch processing of gas, coal or biomass have been certified for use in commercial engines at a blend of up to 50% with conventional jet fuel as of 2009.
  • Hydroprocessed Esters and Fatty Acids (HEFA-SPK). Synthetic fuels derived from the upgrading of oils (e.g., plant oils and animal fats) to hydrocarbons have been certified for use in commercial engines at a blend of up to 50% with conventional jet fuel as of 2011.
  • Hydroprocessed Fermented Sugar-Synthetic Isoparaffins (HFS-SIP). Farnesane derived from hydroprocessed fermented sugars has been certified for use in commercial engines at a blend of up to 10% with conventional jet fuel as of June 2014.

What drop-in alternative jet fuels are on the way to evaluation and approval?
A process has been established to regulate the sequence in which the current roster of alternative fuels and additives will be reviewed by the OEMs. Progression through the process is based on the technical substantiation and test work accomplished by the producer and the task force that has been assisting with the development and review of the product. Several alternative fuel pathways have task force activity in process, and several additional pathways are in development at various stages of fuel readiness level (FRL). CAAFI continues to work with the ASTM community to improve the fuel qualification process, while other industry participants continue to focus resources on timely qualification.

Are alternative fuels economically viable?
The two chief barriers to deployment (in many cases) include the availability of capital to construct the required initial infrastructure, as well as the availability of reasonably priced feedstocks and supply chains. CAAFI, through its members, partners, and work programs are attempting to drive down these barriers to implementation. In the long run, all of the parties involved in CAAFI understand that being the first transportation mode to move forward with drop-in, sustainable, alternative fuels will help ensure aviation's economic viability and environmental acceptability.

Additional studies, including “Near-Term Feasibility of Alternative Jet Fuels” (PARTNER COE and The RAND Corporation) and “Market Cost of Renewable Jet Fuel Adoption in the United States” (PARTNER COE) also discuss the potential economics of alternative aviation fuels.

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