Jet fuel, the power source for aircraft with turbine engines, is a family of specialized, highly refined petroleum products. Mostly based on kerosene, these fuels must meet stringent performance and safety standards for flight. The specific name depends on the fuel’s properties, application, and region, reflecting chemical variations that allow aircraft to operate safely in diverse global conditions.
The Standard Civil Aviation Fuels: Jet A and Jet A-1
The vast majority of commercial passenger and cargo flights worldwide rely on two primary specifications: Jet A and Jet A-1. Both are colorless or straw-colored, kerosene-based fuels that share a nearly identical core chemical structure. Jet A is the standard specification fuel used predominantly in the United States and at a few major Canadian airports.
The most significant difference between the two is their freezing point specification, a safety factor that prevents fuel from solidifying at high altitude. Jet A has a maximum freezing point of -40°C (-40°F). Jet A-1, in contrast, is the global standard for civil aviation and is refined to have a lower maximum freezing point of -47°C (-53°F).
This lower freezing point makes Jet A-1 mandatory for long-haul international flights and routes that regularly cruise at very high altitudes. Both specifications meet the standard ASTM D1655 quality requirements. Jet A-1 often also includes a static dissipater additive to reduce the buildup of static electricity during refueling, which is a minor distinction from Jet A.
Specialized and Military Designations (Jet B and JP Series)
When standard kerosene-based fuels are inadequate, specialized civil and military designations come into use. Jet B is a less common civilian fuel designed for enhanced cold-weather performance in extreme environments like northern Canada and Alaska. This fuel is known as a “wide-cut” fuel because it is a blend of lighter naphtha (similar to gasoline) and kerosene.
Jet B has a very low freezing point, typically around -60°C, which is necessary for operations in Arctic temperatures. However, the inclusion of the more volatile naphtha component means Jet B has a much lower flash point than Jet A or Jet A-1. This increases its flammability risk during storage and handling, meaning it is rarely used unless the extreme cold necessitates its low-temperature properties.
Military aviation uses the “JP” series, short for Jet Propellant, which are fuels with specific U.S. Military specifications. The most common is JP-8, which is essentially the military equivalent of civilian Jet A-1, used widely by NATO forces. JP-8 is a kerosene-based fuel that includes a mandatory package of additives, such as corrosion inhibitors and anti-icing agents, which differentiate it from its commercial counterpart. A separate military fuel, JP-5, is a high flash point kerosene primarily used by the U.S. Navy for aircraft carrier operations. JP-5 is engineered with a higher minimum flash point of 60°C to minimize the risk of fire and explosion in the confined environment of a ship.
The Chemical Distinction: Why Jet Fuel Is Kerosene
Jet fuel is based on kerosene because of the specific chemical properties of this refined petroleum fraction, which is distinct from gasoline. Crude oil is separated into different products, or “cuts,” during the refining process based on their boiling point. Kerosene is a heavier, less volatile cut than gasoline, consisting mostly of hydrocarbons with nine to sixteen carbon atoms per molecule.
The primary reason for using kerosene is its high flash point, which is the lowest temperature at which the fuel vapor can ignite when exposed to a flame. Kerosene-based fuels like Jet A and Jet A-1 must have a flash point above 38°C (100°F). This characteristic makes the fuel far safer to store and handle than highly volatile gasoline, which has a significantly lower flash point and is used in piston-engine aircraft. The lower volatility is especially important for safety in large commercial aircraft and at high altitudes.
The density of kerosene also contributes to performance, as it offers a higher energy density per unit of volume compared to gasoline. This means a given volume of jet fuel contains more stored energy, which is a significant factor for maximizing the range and endurance of long-haul commercial flights. The stringent performance specifications ensure the fuel maintains these qualities across the wide range of temperatures and pressures encountered during flight.