In the mirror universe, in late January 2155, two unnamed NX-class battleships were part of Admiral William Gardner's fleet dispatched to stop Hoshi Sato from becoming the Empress of the Terran Empire. Sato's vessel, the USS Defiant a powerful Federation starship from the future, easily reduced these two battleships to dust. (ENT - Mirror Universe novel: Age of the Empress)
The Romulan War
At some point before 2156, three unidentified NX-class starships were led by Enterprise (NX-01) into battle against a Romulan fleet during the Earth-Romulan War. (ENT - The Romulan War novel: To Brave the Storm)
- On the novel's cover, all of these ships bear the registry NX-01.
- Not all of these sixteen ships have been identified by various media.