Fire barrier for aircraft has an inner, elastic pipe which can be pressurised by feed of pressure medium, and which is surrounded by a flameproof yieldable interlayer. This in turn is surrounded by a resistant outer layer. Preferably the inner pipe consists of a fibre-reinforced silicone elastomer. The interlayer is a yieldable felt flame barrier. The outer layer is resistant, rubber-impregnated glass fibre sheathing, which may also be rubber-coated. The intermediate layer may also be of metal, asbestos or quartz fibres. The barrier prevents fire spreading at the boundary surface between the airframe and an engine.