Constitution-class (Kirk's Enterprise)
The Constitution class was introduced around 2240. At that time the Constitution class was the fastest and most powerful ship type of the fleet and the only one officially designated as starship. 12 ships of this class were in service by the year 2267. Starting with the USS Enterprise in 2271, a number of Constitution-class ships have undergone a complete reconstruction that included new warp nacelles, modification of the engineering hull and "neck", enlargement of the saucer section and a new bridge module. The ships may have been decommissioned at the end of the 23rd century, one of them is displayed in the Starfleet museum.
Source "Ottooo"
The Constitution class was introduced around 2240. At that time the Constitution class was the fastest and most powerful ship type of the fleet and the only one officially designated as starship. 12 ships of this class were in service by the year 2267. Starting with the USS Enterprise in 2271, a number of Constitution-class ships have undergone a complete reconstruction that included new warp nacelles, modification of the engineering hull and "neck", enlargement of the saucer section and a new bridge module. The ships may have been decommissioned at the end of the 23rd century, one of them is displayed in the Starfleet museum.
Source "Ottooo"
