Jet fuel is frequently contaminated with microorganisms that can cause corrosion of fuel tanks. The purpose of this work was to survey the microorganisms currently found in sump water and biofilms of aluminum alloy 2024 (AA2024) fuel tanks containing JP-8 jet fuel. Aerobic and anaerobic bacteria were found in low numbers in sump water, while fungi were rarely present. Numbers of aerobic bacteria and fungi were much higher in biofilms from the tank surface. Common aerobic bacteria were identified belonging to the genera Bacillus and Kurthia. Two fungal isolates were identified as Penicillium funiculosum and Aureobasidium sp. Inoculation of corrosion cells with a mixed microbial community decreased the Ecorr of AA2024 to approximately 80 mV below that of a sterile control. Polarization studies indicated that the microorganisms caused increased anodic current densities, suggesting that the biofilm microorganisms may cause corrosion of fuel tanks.