The Drop-ship was the command module to the Mother-Ship, which has the ability to pilot the Mother-Ship; without actually being attached to it. It was probably programmed by Christopher to detach itself from the mother-ship, due to the fact that it was found underneath Christopher's shack. In the middle of the film, Wikus piloted the drop-ship to be attached with the mother-ship, but in the middle of the process, the ship was shot down and Wikus was captured by the First Reaction Battalion. It appears that Christopher's son has the knowledge to pilot the command module.