From Halopedia, the Halo wiki
The crane ship is modifiable, with the number of cranes being changeable.
Following the end of the Human-Covenant War, the Bustler-class has dominated the skyways of human colonies, offering a plethora of transport options that have helped the rebuilding efforts of the UNSC. Several crane ships were in use at sites over Earth by late 2558. Two were assisting with the "float-out" of an Autumn-class heavy cruiser.