Ice formation in aircraft fuel systems is an ongoing problem with potentially disastrous consequences. Unfortunately, the icing of fuel systems is poorly understood. It is well known that at temperatures below 0 degrees C particles of H(2)O suspended in fuel can exist as crystalline ice or metastable supercooled water. In this paper we show that micron sized water droplets immersed in Jet A-1 aviation fuel can exist in a metastable supercooled state to around -36 degrees C. In fact, the majority of droplets in our experiments froze homogeneously showing that the fuel itself did not catalyse ice formation. We suggest that H2O particles will remain in a supercooled liquid state until they come into contact with a suitable solid surface in an aircraft's fuel system or the temperature falls below the homogeneous freezing limit. (C) 2010 Elsevier Ltd. All rights reserved.