"We must protect the Genesis Ark!"
The Cult of Skaro aquired the Genesis Ark before they fled into the Abyss using a Void Ship. When they emerged on Earth in 2006 PLF they realised they couldn't open the ship. They needed a Time Traveller, and when one of the companions of the Doctor whacked into it during a battle between the Daleks and the Cybermen it opened for them.
Dalek Sec opened the Ark after flying all the way up from the ground to 3000 feet into the air. He then issued a command to the Daleks inside: Exterminate.
The Ark Daleks flew out and begin attacking Humans and Cybermen alike. However, the Doctor opened the Abyss and all the Daleks (and Cybermen too, even though they'd done nothing in comparison) were pulled in. The Ark was lost in the process, destroyed in the fires of the Abyss.