Definition
A kerosene-based turbine engine fuel used in jet and turboprop aircraft, with a maximum freezing point of -47°C. It is the standard turbine fuel for international civil aviation and is widely used outside the United States, where Jet-A (with a -40°C freezing point) is more common.
Plain English
A kerosene fuel made for jet and turboprop engines. Jet-A1 is the version used in most of the world, and it stays liquid at colder temperatures than the U.S. version, Jet-A.
Context Anchor
Seen during aircraft fueling, fuel orders, aircraft manuals, and fuel grade markings on airport fuel trucks or fuel pumps.
Derivation
The 'Jet' prefix simply identifies the fuel as a turbine (jet) engine fuel. The 'A1' designation distinguishes it from related grades — Jet-A (similar but with a higher freezing point) and Jet-B (a wider-cut blend with gasoline-like fractions for very cold climates). The number does not mean 'first quality'; it is a grade label.
Why Pilots Care
Using the correct fuel prevents engine damage, flameouts, and operational restrictions in cold weather.
Intuition Check
Jet-A1 Fuel is not aviation gasoline, and it is not just any fuel used by a jet. It is a specific turbine-engine fuel grade with a very low freezing point.
Example Sentence 1
After landing in Reykjavik, the crew confirmed the fuel truck was loading Jet-A1 before departing on the long over-water leg.
Example Sentence 2
The pilot verified the fuel type on the receipt to confirm it was Jet-A1 Fuel for the international leg.