An air storage plant comprises a storage volume for a pressurized storage fluid, a storage fluid expansion machine and a generator which is arranged with the expansion machine on a common power train. During the start up of the air storage plant, the generator is operated at least temporarily electromotively in order to assist the acceleration of the rotor of the expansion machine. This allows a more rapid acceleration of the expansion machine to the rated rotational speed and, consequently, earlier synchronization and an earlier power output than acceleration caused solely by the storage fluid flowing through.