A saucer fleet consisting of twelve Dalek saucers made up the Dalek Earthforce during the 2150s Dalek invasion of Earth. The Black Dalek's ship was the sole survivor of the fleet when Project Degravitate was thwarted. Badly crippled, the saucer was forced to make a slow return to Skaro, with the Black Dalek reporting the failure to the Dalek Prime. (PROSE: The History of the Daleks)
In the immediate aftermath of the 2150s Dalek invasion of Earth, one Dalek saucer was known to remain operational on Earth, being docked in a London sewer. Though a surviving Dalek bargained with Dalek collaborator Marcus Bray for passage to the saucer, Bray wound up killing the Dalek, later making his way to the saucer in an attempt to contact the Dalek Fleet. With the saucer's antenna damaged, the message failed to send. Following Bray's demise, David Campbell suggested that Susan Foreman use the saucer to escape the anti-alien environment of Earth but she refused, setting the ship to self-destruct. (AUDIO: After the Daleks)