Zeta

Mothership Zeta is an alien ship which appears in the Fallout 3 add-on Mothership Zeta. It comes to the Capital Wasteland to answer the distress call of the crashed alien ship at the Alien Crash Site.

Appearances
Mothership Zeta appears in the Fallout 3 add-on Mothership Zeta.

It can be safe to assume, from the name and from the appearance of the other ship in the last battle, that Mothership Zeta is not the only ship of its kind, and may be the main mothership in our quadrant.