Notes: The Excelsior class was originally designed as a test bed for Starfleet's first experimental transwarp drive. Having been sabotaged before the engines' first transwarp test and having failed in all subsequent attempts, the Excelsior prototype was refitted with a conventional warp drive. As full production started on the Excelsior class, the ship became the mainstay of the fleet in the late 23rd and early 24th centuries, replacing the older Constitution class as the flagship class. The Excelsior class remained in service well into the late 24th century, more then 100 years after if was first launched. A program of continuous enhancements to the ships systems, and being the personal flagship of choice for many admirals, kept the class relevant for its entire life time. The Excelsior class has two major refit variants, the Enterprise-B type and the Lakota type. The Enterprise-B type, commissioned in the late 23rd century, has upgraded sensor and science systems. The Lakota type, commissioned in 2372 right before the outbreak of the Dominion war, brought the weapon and defensive systems up to standard with the Defiant and Sovereign classes.