Aviation Fuel Types Explained: Jet Fuel, Avgas, SAF

Why Aviation Fuel Matters

Fuel is one of the biggest costs for an airline. IATA expects fuel to make up 31.4% of airline operating costs in 2026, up from 25.4% in 2025, after jet fuel prices jumped. IATA's June 2026 outlook assumes jet fuel averages about US$152 a barrel this year, against US$90 in 2025.

Aircraft do not run on regular gasoline. They burn specialized fuels made for extreme conditions: freezing temperatures at cruise altitude, reliable ignition and almost no tolerance for contamination. These fuels power everything from two-seat trainers to widebody jets crossing oceans.

Fuel properties shape how flights are planned. Freezing point affects routes. Flash point sets airport safety rules. Energy content drives range calculations. A Boeing 787 or Airbus A350 burns roughly five to six tonnes of fuel an hour on a long-haul flight, so fuel choice affects both cost and emissions.

How Aviation Classifies Fuels

Aviation fuel falls into three broad groups, based on the engine it feeds.

Turbine fuels (Jet A, Jet A-1, JP-8): Kerosene-based fuels for jet engines, turboprops and turbine helicopters. They burn continuously in the engine's combustion chamber. Cruise temperatures outside can fall to -56°C.

Aviation gasoline (avgas): High-octane gasoline for piston engines in small aircraft and trainers. It needs spark ignition, like a car engine, but a much higher octane rating. Today's mainstream grade, 100LL, contains tetraethyl lead to resist detonation.

Sustainable aviation fuel (SAF): A drop-in jet fuel made from renewable or waste feedstocks. It is chemically very close to conventional jet fuel but has lower lifecycle carbon emissions. Approved blends today are up to 50% SAF with conventional fuel.

The difference matters in practice. Airports use color coding, nozzle sizes and separate infrastructure to stop misfueling.

Jet Fuel Explained

Jet fuel is refined kerosene made for turbine engines. IATA expects airlines to burn about 104 billion gallons of it in 2026. Refineries distill crude oil to get the kerosene cut, remove impurities and add approved additives.

Three characteristics set jet fuel apart:

High flash point (38°C minimum): Jet fuel will not ignite from a static spark during refueling, which cuts the risk of airport fires.

Low freezing point (-40°C for Jet A, -47°C for Jet A-1): The fuel stays liquid at cruise altitude. An aircraft cannot fly if the fuel crystallizes in the tanks.

Steady energy content: The specification requires at least 42.8 MJ/kg, and typical jet fuel delivers about 43 MJ/kg. That predictability makes flight planning accurate.

Even an efficient Airbus A320neo burns roughly two tonnes of fuel an hour in cruise. Across many thousands of daily flights, fuel quality is not negotiable.

Jet A vs Jet A-1: The Critical Difference

Two jet fuel specifications dominate commercial aviation. The difference looks small on paper.

Property	Jet A	Jet A-1
Freezing Point (maximum)	-40°C (-40°F)	-47°C (-53°F)
Primary Usage	United States	International standard
Flash Point	38°C minimum	38°C minimum
Availability	Mainly North America	Worldwide
Energy Content	At least 42.8 MJ/kg	At least 42.8 MJ/kg

Why seven degrees matters: On long flights, fuel in the tanks can get very cold. Jet A starts to form crystals at a higher temperature than Jet A-1, so Jet A-1 gives more margin on polar and other cold, long routes.

Jet A-1 is the fuel stocked at airports outside the United States, so airlines flying internationally mostly use it. U.S. domestic flights commonly use Jet A. The two are close enough that airports in the U.S. also offer Jet A-1 for international traffic.

Aviation Gasoline (Avgas) Explained

Avgas powers piston-engine aircraft: small planes, flight trainers and many warbirds.

It is high-octane gasoline made for aircraft engines. The blue-dyed fuel delivers 100 octane performance, which prevents knock during high-power operations such as a takeoff climb.

Avgas 100LL:

"LL" means "low lead", low compared with older aviation gasoline. It still contains up to 0.56 grams of tetraethyl lead per liter. Lead prevents detonation in high-compression engines at full power.

Avgas burns in spark-ignition engines. Pistons compress the fuel-air mixture, spark plugs ignite it and the expanding gas drives the pistons. This is very different from jet engine combustion.

Color helps prevent mix-ups. Avgas 100LL is dyed blue. Jet fuel is clear to straw-colored. Crews check the fuel type before pumping.

The lead problem:

100LL is the last common transport fuel that still contains lead. Environmental groups have pushed for years for a replacement, but a fuel that works safely in every existing piston engine is hard to make. The FAA approved GAMI's G100UL unleaded avgas by supplemental type certificate in 2022, and other unleaded fuels followed, including Swift Fuels' 100R. A third, UL100E from VP Racing and LyondellBasell, is still in FAA testing. The EAGLE initiative aims to end leaded avgas in the United States by the end of 2030, but supply, cost and mixing questions remain open, and 100LL must stay available during the transition. Find fuel suppliers in our aviation fuel directory.

Aviation Fuel for Helicopters

Most helicopters burn Jet A or Jet A-1, the same fuel as airliners. Turboshaft engines work on the same principle as the turbofans on airliners. Fuel is sprayed into the combustion chamber, mixed with compressed air and burned continuously. The hot gas spins turbines that drive the rotor through a gearbox.

That helps operators. Helicopter operators can refuel at any airport with jet fuel. Militaries simplify logistics by using JP-8, the military version of Jet A-1, in both fixed-wing aircraft and helicopters.

Older piston helicopters burn avgas. The Robinson R44 uses avgas, and the Bell 206 burns jet fuel. Turbine helicopters cost more to buy but use the more widely available fuel.

Military Aviation Fuel Specifications

Military forces use jet fuel variants made for combat and naval operations.

JP-8 (Jet Propellant-8):

The U.S. military standard. It is essentially Jet A-1 with extra additives, including corrosion and icing inhibitors and a lubricity improver.

JP-8 supports the "single fuel forward" policy: the same fuel runs jets, helicopters, ground vehicles and generators. That keeps battlefield logistics simple.

JP-5:

Naval aviation fuel with a higher flash point (60°C minimum, against 38°C for JP-8). Carriers store large amounts of fuel below deck, and the higher flash point cuts fire risk if tanks are damaged.

JP-5 costs more to produce because it needs extra refining. The Navy accepts that cost for shipboard safety.

Military fuel specifications rarely change. JP-8 became the U.S. standard in the 1990s. Switching fuels would mean re-certifying thousands of engines and changing global supply chains.

Sustainable Aviation Fuel (SAF) Explained

SAF is the industry's main near-term tool for cutting carbon emissions. According to IATA (International Air Transport Association), SAF output was about 1 million tonnes in 2024 and 1.9 million tonnes in 2025, or 0.6% of jet fuel use. IATA expects about 2.4 million tonnes in 2026, around 0.8%. Growth is slowing, and IATA blames policy design.

What makes SAF sustainable:

SAF comes from renewable or waste feedstocks, not crude oil. Used cooking oil, fats, agricultural residues, municipal waste and captured carbon dioxide all serve as sources.

The carbon accounting matters more than the chemistry. Sustainable aviation fuel can cut lifecycle CO2 emissions by up to 80% compared with conventional jet fuel, depending on feedstock and process.

SAF is chemically almost the same as petroleum jet fuel, so existing aircraft and engines can use it. No new designs are needed.

Common SAF production pathways:

HEFA (Hydroprocessed Esters and Fatty Acids): Converts waste oils and fats into jet fuel. It makes most of the SAF produced today.

Fischer-Tropsch: Builds hydrocarbons from syngas made from biomass or municipal waste.

Alcohol-to-Jet: Converts ethanol or other alcohols into jet fuel. LanzaJet's Freedom Pines Fuels plant in Georgia is the first commercial-scale ethanol-to-jet facility, and it reported its first production in late 2025.

Power-to-liquid (e-SAF): Combines renewable hydrogen with captured CO2. It can scale a long way but is the most expensive route today.

Current SAF limits:

Price is the biggest barrier. IATA says SAF costs at least twice as much as fossil jet fuel, and up to five times as much in mandated markets.

Supply is far short of demand. Current SAF production is under 1% of jet fuel use.

Blending limits apply. Approvals today allow at most a 50% blend. Flights on 100% SAF are rare tests, and work on approving them continues.

Feedstock is also limited. Used cooking oil and fats can only supply so much, and agricultural residues compete with other uses.

SAF rules in Europe and the UK

Mandates are the main driver of demand. The EU's ReFuelEU Aviation rules required 2% SAF in fuel supplied at EU airports from 2025, rising to 6% in 2030, 20% in 2035 and 70% in 2050, with a separate share for synthetic fuels. The UK mandate started at 2% in 2025 and rises to 10% in 2030 and 22% in 2040. IATA has criticized how both are designed, saying they have not yet raised production enough.

Why Aviation Fuel Costs More Than Diesel

Jet fuel prices move with crude oil and refining margins, and in 2026 they spiked. IATA's June outlook assumes an average of about US$152 a barrel, or roughly US$0.96 a liter. Jet fuel normally sells at a premium to diesel because of tighter specifications and extra handling.

Refining specifications:

Aviation fuel must meet far tighter limits than road diesel. Freezing point, flash point, sulfur, particles and water content all need controlling, which adds refining steps.

Batches are tested before release. Samples go to a lab to check conformance to ASTM D1655 (jet fuel) or DEF STAN 91-091, the UK specification used with it for Jet A-1. Off-spec fuel is not released to aircraft.

Distribution and storage costs:

Airports run dedicated fuel farms with filtration, quality monitoring and contamination controls. Fuel arrives by underground pipeline or in specially certified tankers.

Into-plane refueling equipment is costly. Hydrants, fuel trucks and pumps need regular inspection and maintenance, and those costs reach airlines through fuel prices and fees.

Taxes and surcharges:

Fuel taxes vary by country. Some places exempt jet fuel from road fuel taxes. Others add environmental levies or carbon pricing.

Airlines adjust fares and surcharges as fuel prices move. Cargo operators face the same pressure, and fuel is the largest variable cost in freight operations.

Critical Fuel Properties That Affect Flight Operations

Six fuel properties decide whether a fuel is suitable. Each serves a safety or performance need.

Freezing point: The temperature at which the first wax crystals form in the fuel. Jet A-1's maximum of -47°C allows polar routing and long high-altitude cruise.

Flash point: The lowest temperature at which fuel vapor can ignite near a flame. Higher flash points reduce fire risk during refueling, storage and accidents. Jet fuel's 38°C minimum keeps it stable at normal ambient temperatures.

Energy density: Energy per unit of mass or volume. Jet fuel delivers about 43 MJ/kg. Higher energy density lets an aircraft carry more energy for the same weight, which extends range.

Viscosity: Resistance to flow at different temperatures. Fuel has to move through pumps and nozzles in all conditions.

Lubricity: The fuel's ability to lubricate pumps and injectors. Highly refined, low-sulfur fuels can need lubricity additives to prevent wear.

Thermal stability: Resistance to forming deposits when heated. Fuel circulates through hot engine parts before it burns, and poor stability leaves varnish and carbon that clog nozzles.

Aircraft manufacturers list the approved fuels for each engine. Operators cannot change fuel without engineering approval and sometimes certification testing.

What Happens With Wrong Fuel

Misfueling is a serious hazard. Color coding, placards and training stop most cases, but mistakes still happen.

Jet fuel in a piston engine:

Jet fuel has a very low octane rating, so it knocks and detonates in a spark-ignition piston engine. The engine may run rough at first, lose power and then fail. Several fatal accidents have followed jet fuel being put into piston aircraft. Pilots catch some cases at run-up, but a careful fuel check and sump test before flight is the real defense.

Avgas in a turbine engine:

Most turbine engines are not approved to run on avgas, or only for limited use. The lead leaves deposits on turbine blades and in the combustion chamber, and avgas gives poor lubrication in fuel system parts made for kerosene. If it happens, the maintenance manual usually calls for draining, flushing and inspection.

Prevention:

Jet fuel trucks use a larger nozzle that will not fit most piston aircraft filler necks. Avgas is dyed blue and jet fuel is clear to straw. Fuel trucks carry placards showing the grade, and pilots check the grade, color and quantity before accepting fuel. These layers catch most errors before the engine starts.

Future of Aviation Fuel (2026-2040)

Aviation fuel faces pressure from regulation, fuel security and cost. Several options compete.

SAF scaling:

Sustainable aviation fuel production has to grow many times over to meet mandates and industry goals. Refineries are converting units or building new plants for SAF, but output is growing more slowly than hoped.

Fuels from agricultural and forestry waste are entering production. Algae-based fuels are still in development. Power-to-liquid fuel from renewable electricity and captured CO2 could scale much further, but it is costly today, and cost reductions depend on cheaper renewable power and carbon pricing.

Hydrogen:

Hydrogen fuel cells or direct combustion could remove carbon emissions from flight. Airbus had targeted a hydrogen airliner (ZEROe) for 2035, but it has since pushed those plans back.

The challenges are large. Hydrogen has low energy density by volume, so aircraft need big tanks. Airports lack production, storage and refueling systems. Early use is likely to be on regional routes.

Electric and hybrid aircraft:

Battery-electric aircraft suit short-range flights, mainly trainers and small commuter aircraft.

Battery energy density limits larger aircraft. Good lithium-ion cells store roughly 0.9 MJ/kg (about 250 Wh/kg). Jet fuel holds about 43 MJ/kg. With foreseeable technology that rules out battery-powered widebody jets. Hybrid-electric systems that pair batteries with turbines are being tested for regional aircraft.

Regulation:

SAF blending mandates in the EU and UK are in force, and other regions use carbon pricing or emissions trading that favors lower-carbon fuel.

Certification processes are adapting to approve 100% SAF operations. Test programs check long-term material compatibility with pure SAF.

The most likely 2040 picture mixes solutions. SAF fuels long-haul flights, hydrogen or electric power covers some regional and small aircraft, and conventional jet fuel stays where alternatives do not fit.

Frequently Asked Questions

What fuel do commercial airplanes use?

Airliners burn kerosene-based turbine fuel, mostly Jet A-1 outside the United States and Jet A inside it. Jet A-1 has a maximum freezing point of -47°C, a minimum flash point of 38°C and an energy content of at least 42.8 MJ/kg. Jet A freezes at -40°C.

Is jet fuel the same as diesel?

They are similar petroleum products but not the same. Both come from middle-distillate fractions of crude oil. Jet fuel meets much stricter limits on freezing point, particles and thermal stability. Some diesel engines can run on jet fuel, but jet engines should not run on road diesel because it does not meet the specification.

Why does aviation fuel not freeze easily?

Jet fuel is a blend of hydrocarbons chosen for a low freezing point. Jet A-1 stays liquid down to -47°C, so it handles cruise altitudes where the outside air is around -56°C. Fuel in the tanks stays warmer than the outside air, and aircraft monitor fuel temperature in flight.

Can planes use biofuel?

Yes. Aircraft fly on sustainable aviation fuel (SAF) made from biological and waste sources. It works in existing aircraft without changes, in blends of up to 50% with conventional fuel. Supply and price, not technology, are the main limits.

What fuel do small planes use?

Small piston aircraft burn avgas, usually 100LL. It contains lead to prevent knock and is dyed blue. Some small aircraft have turbine engines and burn Jet A. The engine type decides the fuel, not the size of the aircraft.

Is SAF widely used today?

Not yet. IATA puts 2025 production at 1.9 million tonnes, or 0.6% of jet fuel use, and expects about 0.8% in 2026. Price and limited production hold it back, and mandates in Europe and the UK are now pushing airlines to buy more.

Why is avgas still leaded?

High-compression piston engines need lead's anti-knock effect at full power, and an unleaded fuel has to work safely in the whole existing fleet. Unleaded fuels such as G100UL and 100R now have FAA approval for many aircraft, and the U.S. goal is to end leaded avgas by the end of 2030. The change is still under way.

Do helicopters use special fuel?

Most modern helicopters burn Jet A or Jet A-1. Only older piston helicopters need avgas. Military helicopters use JP-8, which is essentially Jet A-1 with extra additives.

Aircraft Fuel Efficiency and Selection

Fuel cost shapes aircraft choice. Airlines pick aircraft partly on fuel burn and operating efficiency.

New aircraft are commonly 15% to 25% more efficient than the models they replace. The Pratt & Whitney geared turbofan engine gets its savings from better engine efficiency.

Long-range design revolves around fuel capacity and burn rate. Makers tune wings, engines and aerodynamics to cut consumption, and every kilogram saved multiplies across thousands of flights.

Fuel availability affects routing. Airlines avoid airports without proper fuel infrastructure. Where local fuel is scarce, costly or of doubtful quality, crews practice tankering, which means carrying extra fuel from the previous stop.

Fuel hedging protects some airlines from price swings. IATA says airlines had hedged roughly one third of expected 2026 fuel use. Carriers that do not hedge gain when prices fall and pay more when they spike.

Efficiency gains keep coming from better engines, materials and aerodynamics. Combined with SAF adoption, they cut both costs and emissions. For environmental specialists, see our aviation environmental services directory.

Sources: IATA Global Outlook for Air Transport (June 2026) and SAF fact sheet; EASA ReFuelEU Aviation summary; FAA unleaded avgas transition plan and EAGLE updates (2026); ASTM D1655; DEF STAN 91-091; LanzaJet announcements. Checked 26 October 2026.