Jet fuel is a highly refined, kerosene-based fuel designed to power the turbine engines of modern aircraft. It must meet stringent performance and safety standards to function reliably across a wide range of temperatures and altitudes. Its primary purpose is to provide consistent, clean-burning energy for commercial airliners and military jets. The physical characteristics of jet fuel, including its color, are tightly controlled to ensure quality and prevent dangerous errors during fueling.
The Standard Color of Jet Fuel
The most commonly used jet fuels, Jet A and Jet A-1, are typically clear or possess a very light straw-yellow tint. This near-colorless appearance results from the extensive refining process applied to the kerosene base stock, which removes impurities and colored compounds, leaving behind a highly pure hydrocarbon mixture.
The faint amber or straw hue sometimes visible is not an intentional color addition but a function of trace, naturally occurring aromatic compounds. These compounds are present in the crude oil source and are not completely removed during distillation and purification. This slight coloration does not impact the fuel’s performance.
International specifications for Jet A and Jet A-1 do not permit the addition of color dyes. This standard ensures that any significant color change immediately signals a potential contamination issue, such as mixing with a different, dyed fuel grade. Quality control checks involve visually inspecting the fuel for clarity and color before fueling an aircraft. A darker or cloudy appearance indicates contamination by water, sediment, or another petroleum product.
Why Jet Fuel Is Not Always Clear
While commercial Jet A and Jet A-1 are clear to straw-colored, other specialized jet fuel grades show slight color variations. Jet B, a less common grade used in extremely cold regions, is a blend of naphtha and kerosene that is more volatile than Jet A. This mixture is also typically clear or straw-colored, though its different chemical composition may result in a marginally different natural tint.
Military jet fuels, such as JP-8 and JP-5, are kerosene-based but contain performance-enhancing and safety additives. These additives, including corrosion inhibitors, anti-icing agents, and static dissipaters, are usually colorless. JP-8, the military equivalent of Jet A-1, is described as colorless or slightly yellow, confirming the standard appearance is maintained despite the added compounds.
Key Differences from Other Fuels
The clear or pale straw color of jet fuel stands in stark contrast to the vivid dyes used in other types of aviation and ground fuels, a difference that serves a safety function. Aviation gasoline (Avgas), which powers smaller piston-engine aircraft, is intentionally dyed in bright colors for immediate identification. For example, the common Avgas 100LL is dyed blue.
This deliberate color coding is a preventative measure against misfueling, which can be catastrophic in aviation. Accidentally putting kerosene-based jet fuel into a piston engine designed for gasoline, or vice versa, would lead to engine failure. The clear difference between the blue of Avgas and the clear color of Jet A provides an instant visual check for ground crews. Jet fuel is also visually distinct from tax-dyed red diesel or brightly colored automotive racing fuels, minimizing the risk of cross-contamination.