A fuel composition useful for operating a jet engine or a diesel engine containing a petroleum derived kerosene fuel and a Fischer-Tropsch derived kerosene fuel is provided. The Fischer-Tropsch derived kerosene fuel contains normal and iso-paraffins in a weight ratio of greater than 1:1 and/or the freeze point of the composition is lower than the freeze points of both of the petroleum derived kerosene fuel and the Fischer-Tropsch derived kerosene fuel.