Airplane having: main propulsion jet engines and a first fuel supply for the main propulsion jet engines, a spare auxiliary propulsion jet engine and a second fuel supply for the spare auxiliary propulsion jet engine, wherein the second fuel supply is completely separate from the first fuel supply and dedicated for supplying the spare auxiliary propulsion jet engine only, and wherein the spare auxiliary propulsion jet engine can be switched on independently from the main propulsion engines; characterised in that the airplane is further provided with protective cover elements covering air intake and outlet openings of the spare auxiliary propulsion jet engine during flights, and controllable to be released during flight, the protective cover elements having normal protection positions in which they protect the spare auxiliary propulsion jet engine, and having release positions in which they do not cover the corresponding spare auxiliary propulsion jet engine openings; wherein the airplane has a normal flight mode in which the main propulsion jet engines are used and the spare auxiliary propulsion jet engine is not used such as to ensure that this engine remains ready for operation when a dramatic event occurs that affects all running engines, and wherein the protective cover elements are in their normal protection positions; wherein the airplane has an emergency flight mode in the case of a failure of all main propulsion engines, wherein the protective cover elements are in their release position and the spare auxiliary propulsion jet engine is used to provide thrust to decrease the plane's descent angle. main propulsion jet engines and a first fuel supply for the main propulsion jet engines, a spare auxiliary propulsion jet engine and a second fuel supply for the spare auxiliary propulsion jet engine, wherein the second fuel supply is completely separate from the first fuel supply and dedicated for supplying the spare auxiliary propulsion jet engine only, and wherein the spare auxiliary propulsion jet engine can be switched on independently from the main propulsion engines; characterised in that the airplane is further provided with protective cover elements covering air intake and outlet openings of the spare auxiliary propulsion jet engine during flights, and controllable to be released during flight, the protective cover elements having normal protection positions in which they protect the spare auxiliary propulsion jet engine, and having release positions in which they do not cover the corresponding spare auxiliary propulsion jet engine openings; wherein the airplane has a normal flight mode in which the main propulsion jet engines are used and the spare auxiliary propulsion jet engine is not used such as to ensure that this engine remains ready for operation when a dramatic event occurs that affects all running engines, and wherein the protective cover elements are in their normal protection positions; wherein the airplane has an emergency flight mode in the case of a failure of all main propulsion engines, wherein the protective cover elements are in their release position and the spare auxiliary propulsion jet engine is used to provide thrust to decrease the plane's descent angle.