Jet fuel, Aviation Turbine Fuel (ATF), or Avtur is a type of fuel designed for use in aircraft powered by gas-turbine engines. It is clear to straw-coloured in appearance. The most commonly used fuels for commercial aviation are Jet A and Jet A-1 which are produced to a standardized international specification. During the refining process only 8% of the crude oil is made up of Jet fuel.