A jet engine, which is suited for hypersonic intake velocities, has a rotating cascade in the intake duct for decelerating the hypersonic flow. The blade angles Beta 1, Beta 2 of the rotating cascade, the circumferential speed U of the rotor and the deceleration Delta w of the relative cascade flow are matched in accordance with cos Beta 2 (U . cos Beta 1)/(U Delta W . cos Beta 1), to ensure an axial direction of the absolute flow at the rotor cascade exit. A stationary vane cascade can be arranged downstream of the rotor cascade, in the case of high blade camber, for further deceleration and axial straightening of the flow. The intake rotor can be coupled to an engine accessory power unit or to a compressor arranged downstream of the intake. Controllable flaps can be provided to route the gas jet leaving the engine combustion chamber either to a turbine arranged downstream for driving the compressor or directly to the engine outlet nozzle. The intake rotor can also be coupled to an acceleration cascade arranged downstream of the combustion chamber; the acceleration cascade can also be preceded by a stationary vane cascade.