Paraffinic hydrocarbons from hydroprocessed esters and fatty acid (HEFA), synthetic paraffinic kerosene (alc. to jet ATJ) and their blends with fossil jet fuel were tested for d., viscosity (at -20 degrees C and -40 degrees C), fractional compn., arom. (esp. naphthalenes) cored. content, non-smoking flame height, flash point and lubricity. The min. required content of arom. compds. in mixts. was 8% by vol. An increase in the viscosity of mixts. with both HEFA and ATJ was obsd. as compared to fossil jet fuel. With an increase in the content of synthetic components in the mixts., the flash point and height of the non-smoking flame increased, but the content of naphthalenes decreased. The lubricity of fuels met the assumed requirements.