A cartridge for an aerosol-generating system, the cartridge comprising: a cartridge main body comprising at least one cartridge air outlet; a storage container within the cartridge main body, the storage container containing a supply of liquid aerosol-forming substrate; a heating element disposed at a first end of the cartridge main body, the heating element being in fluid communication with the storage container; and a cartridge cap comprising: at least one cartridge air inlet; a top portion configured to cover the first end of the cartridge main body and the heating element; and a side portion extending from the cartridge cap top portion and over a part of a side portion of the cartridge main body, and wherein, the cartridge cap side portion comprises an engagement portion, configured to releaseably engage with a corresponding portion of the cartridge main body, and wherein, when the engagement portion is disengaged from the cartridge main body the cartridge cap is configured to move relative to the cartridge main body between: a first position, in which one or both of the cartridge cap and the cartridge main body block air from flowing from the cartridge air inlet to the cartridge air outlet, via the heating element; and a second position, in which an airflow path exists from the cartridge air inlet to the cartridge air outlet, via the heating element. a cartridge main body comprising at least one cartridge air outlet; a storage container within the cartridge main body, the storage container containing a supply of liquid aerosol-forming substrate; a heating element disposed at a first end of the cartridge main body, the heating element being in fluid communication with the storage container; and a cartridge cap comprising: at least one cartridge air inlet; a top portion configured to cover the first end of the cartridge main body and the heating element; and a side portion extending from the cartridge cap top portion and over a part of a side portion of the cartridge main body, and at least one cartridge air inlet; a top portion configured to cover the first end of the cartridge main body and the heating element; and a side portion extending from the cartridge cap top portion and over a part of a side portion of the cartridge main body, and wherein, the cartridge cap side portion comprises an engagement portion, configured to releaseably engage with a corresponding portion of the cartridge main body, and wherein, when the engagement portion is disengaged from the cartridge main body the cartridge cap is configured to move relative to the cartridge main body between: a first position, in which one or both of the cartridge cap and the cartridge main body block air from flowing from the cartridge air inlet to the cartridge air outlet, via the heating element; and a second position, in which an airflow path exists from the cartridge air inlet to the cartridge air outlet, via the heating element. a first position, in which one or both of the cartridge cap and the cartridge main body block air from flowing from the cartridge air inlet to the cartridge air outlet, via the heating element; and a second position, in which an airflow path exists from the cartridge air inlet to the cartridge air outlet, via the heating element.