This article reports on a study of cratering effects in thin anti-icing films designed to protect aircraft surfaces from snow and ice accumulation while the aircraft is on the ground awaiting takeoff. These fluids primarily consist of a glycol used as a freezing point depressant, water, and to a small extent thickening and wetting agents. Craters formed in these films represent local areas where the film thickness is dramatically reduced and can lead to premature failure of the film. This phenomenon was found to be driven by surface tension gradients at the film surface that cause surface movement and drag the underlying fluid. These surface tension gradients are formed because the surfactants being used in the antiicing fluids are more effective in water-rich solutions than in glycol-rich solutions. Experimental results are given that illustrate this behavior of the surfactant and numerical work is presented to show that the magnitude of surface tension differences obtained is adequate to drive the phenomenon.