Kerosene, refined into Jet-A or Jet A-1 fuel, is the standard power source for nearly all turbine-engine aircraft globally. Its widespread adoption stems from a precise combination of physical, chemical, and logistical characteristics that make it uniquely suited for aviation. Jet fuel provides the most effective balance of energy output, operational safety, and worldwide availability the industry requires. Its reliable performance and inherent safety advantages over more volatile alternatives cement its role as the industry’s fuel source.
High Energy Density and Mass Efficiency
In aviation, the mass of the fuel is the primary constraint, making gravimetric energy density (energy per unit of mass) a paramount specification. Jet fuel consists of hydrocarbon chains longer than those in gasoline. While this results in a slightly lower energy content per pound, kerosene-type fuel still offers around 43 to 48 megajoules per kilogram (MJ/kg).
The primary advantage of jet fuel lies in its volumetric energy density (energy per unit of volume). Kerosene is denser than gasoline, meaning a fixed volume, such as a wing tank, can hold more mass of fuel and thus more total energy. Since the physical space for fuel tanks is fixed and limited, this higher volumetric energy content maximizes the aircraft’s range and payload capacity.
Low Temperature Performance and Thermal Stability
Jet fuel must function reliably across an enormous range of temperatures, from the extreme cold of high-altitude flight to the intense heat within the engine system. At cruising altitudes, temperatures drop well below freezing, risking fuel solidification. To prevent this, jet fuel specifications mandate a low maximum freezing point; for Jet A-1, this is -47°C, ensuring the fuel remains liquid and flows freely to the engines.
The fuel also serves as a coolant for the engine’s oil and hydraulic systems before combustion, exposing it to significant heat. This requires high thermal stability, which is the fuel’s resistance to chemical breakdown when heated. Breakdown forms solid deposits, known as coking, which can clog fuel nozzles and filters, leading to engine malfunction.
Safety Profile and Flash Point Requirements
The flash point of a liquid is the lowest temperature at which its vapors can be ignited by an external spark or flame. Kerosene-type jet fuel, such as Jet A and Jet A-1, has a high flash point, typically set at a minimum of 38°C (100°F). This is significantly higher than the flash point of gasoline, which can be as low as -43°C.
This higher flash point makes jet fuel a “combustible” liquid rather than a highly volatile “flammable” liquid, greatly enhancing safety during ground operations and in the event of an accident. Kerosene is less likely to ignite from a simple spark or heat source during refueling or a minor leak. Its low volatility resists forming an easily ignitable vapor cloud in a crash scenario, improving survivability by preventing immediate, explosive fires.
Operational Reliability and Global Supply Chain
Kerosene is a middle distillate, a common fraction produced during the atmospheric distillation of crude oil in refineries. This makes it an abundant and economically viable product to manufacture globally. Its consistent presence in the refining process helps establish a reliable and cost-effective supply chain necessary for an industry that consumes millions of gallons of fuel daily.
Beyond its role as a power source, the fuel must also act as a lubricant for the high-speed pumps and flow control units within the engine’s fuel delivery system. Kerosene possesses the necessary lubricity, or lubricating properties, to protect these sensitive components from premature wear. The standardization of Jet-A and Jet A-1 specifications worldwide ensures that any aircraft can land and refuel almost anywhere on the planet with a product of predictable and consistent quality, facilitating the seamless logistics of global air travel.