A cartridge assembly for use in an aerosol-generating system, the cartridge assembly comprising: a cartridge comprising: a cartridge body having a first side defining a first recess and a second side defining a second recess; and a cartridge cover comprising: a cartridge cover cavity in which the cartridge body is slidably received; a cartridge cover opening at a downstream end of the cartridge cover cavity; a cartridge cover wall portion extending across an upstream end of the cartridge cover cavity and comprising a cartridge cover air inlet; and an actuation aperture in the cartridge cover wall portion for receiving an actuation portion of an aerosol-generating device; and a mouthpiece comprising a mouthpiece cavity in which a downstream end of the cartridge is received; wherein the cartridge is configured so that, when an actuation portion of an aerosol-generating device is received against the cartridge body through the actuation aperture, the cartridge body slides within the cartridge cover cavity from a first position to a second position; wherein, in the first position, an upstream end of the cartridge body abuts the cartridge cover wall portion and obstructs the cartridge cover air inlet, and a downstream end of the cartridge body abuts a downstream end of the cartridge cover and obstructs the cartridge cover opening; and wherein, in the second position, the upstream end of the cartridge body is spaced apart from the cartridge cover wall portion and the downstream end of the cartridge body is spaced apart from the downstream end of the cartridge cover so that the cartridge cover air inlet is in fluid communication with the cartridge cover opening via the first recess and the second recess. a cartridge comprising: a cartridge body having a first side defining a first recess and a second side defining a second recess; and a cartridge cover comprising: a cartridge cover cavity in which the cartridge body is slidably received; a cartridge cover opening at a downstream end of the cartridge cover cavity; a cartridge cover wall portion extending across an upstream end of the cartridge cover cavity and comprising a cartridge cover air inlet; and an actuation aperture in the cartridge cover wall portion for receiving an actuation portion of an aerosol-generating device; and a cartridge body having a first side defining a first recess and a second side defining a second recess; and a cartridge cover comprising: a cartridge cover cavity in which the cartridge body is slidably received; a cartridge cover opening at a downstream end of the cartridge cover cavity; a cartridge cover wall portion extending across an upstream end of the cartridge cover cavity and comprising a cartridge cover air inlet; and an actuation aperture in the cartridge cover wall portion for receiving an actuation portion of an aerosol-generating device; and a cartridge cover cavity in which the cartridge body is slidably received; a cartridge cover opening at a downstream end of the cartridge cover cavity; a cartridge cover wall portion extending across an upstream end of the cartridge cover cavity and comprising a cartridge cover air inlet; and an actuation aperture in the cartridge cover wall portion for receiving an actuation portion of an aerosol-generating device; and a mouthpiece comprising a mouthpiece cavity in which a downstream end of the cartridge is received; wherein the cartridge is configured so that, when an actuation portion of an aerosol-generating device is received against the cartridge body through the actuation aperture, the cartridge body slides within the cartridge cover cavity from a first position to a second position; wherein, in the first position, an upstream end of the cartridge body abuts the cartridge cover wall portion and obstructs the cartridge cover air inlet, and a downstream end of the cartridge body abuts a downstream end of the cartridge cover and obstructs the cartridge cover opening; and wherein, in the second position, the upstream end of the cartridge body is spaced apart from the cartridge cover wall portion and the downstream end of the cartridge body is spaced apart from the downstream end of the cartridge cover so that the cartridge cover air inlet is in fluid communication with the cartridge cover opening via the first recess and the second recess.