Engine nacelle for a turbofan engine, which engine nacelle has: - a nacelle wall which has an inner side (22, 32) and an outer side (21, 31), wherein the nacelle wall has an inlet lip which is formed on the upstream end of the engine nacelle, and - an engine inlet which takes in the air required for an associated engine and which is delimited by the inner side (22, 32) of the nacelle wall, wherein - the nacelle wall has a fixed downstream section and has an upstream section which is displaceable in an axial direction, and the displaceable upstream section is displaceable between a first, upstream position and a second, downstream position, - the engine nacelle, in the first position of the displaceable section, forms a ring-shaped auxiliary flow duct which extends from the outer side of the nacelle wall to the engine inlet and which is in this case formed such that, during the operation of a turbofan engine which comprises the engine nacelle, ambient air can flow via the auxiliary flow duct from the outside of the nacelle wall upstream of the fan of the associated turbofan engine into the engine inlet, wherein the downstream end of the auxiliary flow channel ends upstream of the fan of the associated turbofan engine, and - the ring-shaped auxiliary flow channel is closed in the second position of the displaceable section, characterized by a ring-shaped seal (5, 50) which is formed between the fixed section and the displaceable section of the nacelle wall, wherein, - in the second position of the displaceable section, the fixed section, the ring-shaped seal (5, 50) and the displaceable section adjoin one another, - the ring-shaped seal (5, 50) has at least one hollow chamber (53, 54), and - the at least one hollow chamber (53, 54) is suitable and designed to be variable in terms of its shape during operation by adjustment of the degree of filling thereof. - a nacelle wall which has an inner side (22, 32) and an outer side (21, 31), wherein the nacelle wall has an inlet lip which is formed on the upstream end of the engine nacelle, and - an engine inlet which takes in the air required for an associated engine and which is delimited by the inner side (22, 32) of the nacelle wall, wherein - the nacelle wall has a fixed downstream section and has an upstream section which is displaceable in an axial direction, and the displaceable upstream section is displaceable between a first, upstream position and a second, downstream position, - the engine nacelle, in the first position of the displaceable section, forms a ring-shaped auxiliary flow duct which extends from the outer side of the nacelle wall to the engine inlet and which is in this case formed such that, during the operation of a turbofan engine which comprises the engine nacelle, ambient air can flow via the auxiliary flow duct from the outside of the nacelle wall upstream of the fan of the associated turbofan engine into the engine inlet, wherein the downstream end of the auxiliary flow channel ends upstream of the fan of the associated turbofan engine, and - the ring-shaped auxiliary flow channel is closed in the second position of the displaceable section, - in the second position of the displaceable section, the fixed section, the ring-shaped seal (5, 50) and the displaceable section adjoin one another, - the ring-shaped seal (5, 50) has at least one hollow chamber (53, 54), and - the at least one hollow chamber (53, 54) is suitable and designed to be variable in terms of its shape during operation by adjustment of the degree of filling thereof.