Abstract: The present invention relates to methods for ground handling, controlling the altitude and for increasing the longitudinal stability of airships. The invention involves an airship hull or envelope to enclose air-filled ballonets and a lifting gas. The buoyancy obtained may be changed by varying the air pressure in the ballonets, thus forcing compression or allowing expansion of the lifting gas. Suitable air pump and valve means are provided to allow two different levels of pressure differential in the ballonets. The buoyancy of the airship is decreased during ground handling and during descent and increased during climb. The airship cruise altitude is slightly above pressure height.