The invention relates to a flame retardant composition, particularly designed for fire fighting with aerial means. The retardant composition comprises a liquid ammonium polyphosphate of chain length with a value of n between 2 and 3, n being the number of condensation groups, and an ammonium polyphosphate in powder form in suspension, with a chain length with a value of n between 100 and 1500. In addition to the above, the flame retardant composition comprises corrosion inhibitors, in particular zinc orthophosphate dihydrate, and at least one surfactant agent as wetting agent or dispensing agent, an organic or inorganic thickening agent and at least one coloring agent.