Major aircraft fires must be controlled extremely rapidly if lives are to be saved, and since all fire-fighting material has to be carried to the fire, such fires demand a fire-fighting agent of high weight effectiveness. This note describes an investigation of the performance of light-water, a synthetic perfluorinated surface active foaming agent, on the extinction of simulated aircraft fires of areas up to 325 m2 (3500 ft2) burning AVTUR (JP1) and AVTAG (JP4) fuels. It compares this performance with that of regular protein foam, and that of a "fortified" protein foam containing synthetic surface-active agents. It shows that the "light water" is up to twice as effective as regular protein foam, in terms of weight of foaming solution to control the fire, and that the fortified protein foam is about 25% more effective than regular protein foam. The light water foam only showed about one third the resistance of the protein foam to the re-establishment of flame over the area, once a fairly large area of fire was re-opened.