What fuel do most modern hot-air balloon burners use?

Most modern hot-air balloon burners use propane as their fuel.

Propane is stored as a pressurized liquid in tanks carried in or beside the basket. When released through the burner system, it vaporizes and mixes with air before burning in a powerful flame. The pilot directs that flame into the envelope to raise the temperature of the air inside.

Propane became especially useful because it is energy-dense, widely available, and relatively easy to store in liquid form. The tanks are connected to hoses and burner valves, allowing the pilot to control the size and duration of each blast. Pilots often use short burns to adjust altitude rather than keeping the flame continuously lit.

Early balloons used fires fed by materials such as straw, wood, and wool. Those open fires were difficult to control and created serious risks. Modern propane burners provide much more consistent heat, but ballooning remains weather-dependent because wind, rain, and visibility strongly affect operations.