Why Do Aircraft Use Kerosene (Jet Fuel)?

Today, we take it for granted that jet aircraft burn kerosene. But in the early days of aviation, planes ran on the same gasoline as your car. Why did the menu change so completely? This history is not just a story of fuel technology-it's a saga of safety, performance, and engineering trade-offs.

Part 1: The Piston Era (1903–1940s) – Gasoline's Brief Reign
The Wright Brothers' first flight used gasoline. Early aircraft all used piston engines, similar to car engines, so gasoline was the natural choice.

Problems soon emerged:

Engine Knocking (Detonation): To increase power, pilots needed higher compression ratios, but ordinary gasoline would self-ignite and detonate. This could reduce power or even shatter cylinders.

High Volatility: Gasoline evaporates easily at room temperature, creating flammable vapors. During WWI and WWII, many aircraft caught fire or exploded on the ground during refueling due to static sparks.

Carburetor Icing at Altitude: Water vapor in the intake air would freeze in the carburetor at high altitude, blocking the engine. Early pilots sometimes had to manually drip antifreeze into the carburetor.

In the 1930s, a solution was found in the form of Aviation Gasoline, also known as Avgas. By adding a chemical called tetraethyl lead to the fuel, the octane rating was increased from 40 to 100/130 or even higher. This new fuel, Avgas, was used to power some of the most iconic planes of World War II, including the P-51 Mustang fighter and the B-29 Superfortress bomber. However, as time went on, the toxic effects of lead became a major concern, and the limits of octane ratings were reached, prompting engineers to search for alternative solutions.

Part 2: The Jet Revolution (1940s) – Gasoline is Condemned
The jet engine was born in the 1940s (Germany's He 178, Britain's Gloster E.28/39). Its combustion chamber required a fuel that could:

Be injected at high pressure and burn stably.

It can flow easily even when it's really, really cold - we're talking -50°C or -58°F, which is the kind of temperature you'd experience when you're up at cruising altitude.

Lubricate the high-pressure fuel pump plunger.

Gasoline failed all three tests.

Property Gasoline Jet Engine Requirement
Flash Point ~ -43°C (-45°F) - Extremely Flammable > 38°C (100°F) for safety
Low-Temp Flow Solidifies around -40°C (-40°F) Must flow below -50°C (-58°F)
Lubricity Very poor (dry) Needs some lubricity for fuel pump
Diesel fuel was not considered a good option either. One reason is that it's really thick and doesn't break down easily, which makes it hard to use in engines. Also, when it's cold, diesel fuel gets even thicker and flows slowly, kind of like honey. And to make matters worse, it can leave behind yucky carbon deposits that can damage the engine over time.

Engineers turned their attention to kerosene, which is often considered the perfect middle ground - not too light like gasoline, not too heavy like diesel.

Part 3: The Triumph of Kerosene (1950–1960s) – Setting the Standard
Britain led the way: In the late 1940s, de Havilland developed a high-purity kerosene for the "Comet" jet airliner, naming it Avtur (Aviation Turbine Fuel) . When the Comet first flew in 1952, it burned kerosene.

The United States took a trial and error approach to finding the right fuel. At first, the US Air Force used a "wide-cut" fuel called JP-1, which was similar to heavy gasoline. However, this fuel caused a lot of problems, including coking deposits and frequent fire hazards from leaks. Later, during the Korean War, the F-86 Sabre jet used JP-4, a mix of gasoline and kerosene. While JP-4 was less likely to freeze, it was highly flammable, which led to many accidents on the ground.

The final solution:

Military: JP-8 (adopted from the 1970s onward) – essentially kerosene with small amounts of anti-static and anti-icing additives.

For planes, there are two main types of fuel: Jet A and Jet A-1. Jet A is used in the US and has a high freeze point, while Jet A-1 is used in other countries and can handle really cold temperatures, as low as -47°C or -53°F. Over time, these two types of fuel became the standard for the whole world.

We use a huge amount of jet fuel every year - about 300 billion liters. And get this, almost all jet planes, a whopping 99%, run on fuels made from kerosene.

Part 4: Why Kerosene Won – A Technical Review
When the flash point of a fuel is high, above 38°C or 100°F, it means that it can't catch fire from a naked flame when it's at room temperature. This is really important because it lowers the risks of fires when fuel is being handled on the ground or if there's a leak during a flight.

Low Freeze Point (< -47°C / -53°F): Remains fluid at typical intercontinental cruise altitudes (around -50°C / -58°F).

Thermal Stability: Does not easily decompose or form carbon deposits in fuel-oil heat exchangers (operating above 150°C / 302°F), which could clog precision fuel nozzles.

Favorable Energy Density: Has about 12% higher volumetric energy density than gasoline, translating to longer range.

Appropriate Lubricity: Provides just enough lubrication for high-pressure fuel pump plungers (though modern ultra-low-sulfur kerosene sometimes requires added lubricity improvers).

Part 5: The Future – How Much Longer Will Kerosene Dominate?
Challenger 1: Sustainable Aviation Fuel (SAF)
Sustainable aviation fuel, or SAF, is created from things like waste oils, trash from cities, or leftovers from farms. It's very similar to the kerosene we get from fossils, so we can mix it with that fuel right now - up to half and half. The big plan is to have no carbon emissions at all by the year 2050.

Challenger 2: Liquid Hydrogen (LH₂)
Airbus plans to introduce hydrogen-powered airliners by 2035. Hydrogen has zero carbon emissions and very high gravimetric energy density. However, its volumetric density is extremely low, requiring large, heavy cryogenic tanks. Challenges like hydrogen embrittlement and explosion risks remain.

Challenger 3: Battery-Electric
Only feasible for small regional aircraft flying under 500 km (310 miles). Battery energy density is about 50 times lower than kerosene, making it impossible for large, long-haul jets.

For a long time to come, probably until 2050, big planes will still be using kerosene or a similar fuel made in a lab. This type of fuel has been around for a while, but it's really good at what it does and it's hard to find something better. It's like the standard language of flying, old but still the best choice.

Epilogue: A Telltale Detail
Frank Whittle, a British engineer, patented the jet engine back in 1930. He initially used gasoline in his test rigs, but it didn't quite work out as planned. The engine would vibrate violently and the flame cans would get burnt. Frustrated, Whittle decided to give kerosene a try - and it was a game-changer. The engine started running smoothly right away. From then on, it was clear that gasoline wasn't the best choice for large aircraft. It was just too volatile, too fast, and too dangerous. On the other hand, kerosene proved to be a reliable partner for flying. Its slow and steady pace made it the perfect fit for the skies.