The effect of additives - surfactants (SF) - on the water-separating properties of jet fuels. These additives significantly worsen the "fuel-water reaction" index. Methods of fuel flooding simulating the conditions of formation of water-fuel microemulsions during storage, shipment, and use are developed. Data on the effect of the nature of the fuel on the settling rate of microemulsions are reported. Water-fuel microemulsions, form when temperature fluctuations are stable for more than 100 h, which favors formation of aqueous sludges in aircraft tanks.