A combustion system for performing stable combustion and flame stabilization at high altitudes is described. A primary liquid hydrocarbon fuel is atomized and vaporized within the main combustor chamber to produce a primary fuel vapor. When the combustion system operates at a high altitude, a secondary gaseous fuel is fed into the inlet air port such that the secondary fuel mixes with air, thereby enabling the mixture of the air and the secondary fuel to combust in a catalytic reactor to produce high temperature, oxygen-rich gases that flow into the main combustor chamber. Proper proportional amounts of the two fuels are determined as a function of altitude.