FSD: Enterprise - NCC-1701-A Constitution-class

The second starship Enterprise was launched in 2286 on stardate 8442.5 from the San Francisco Fleet Yards under the command of demoted admiral, Captain Kirk. The command was given by the Federation Council in gratitude for saving Earth from the alien probe. Starfleet renamed the USS Yorktown NCC-1717 to Enterprise.

In 2287, the Enterprise-A was launched into duty before it was ready when diplomatic representatives on Nimbus III were held hostage by Sybok, a renegade Vulcan and Captain Spock's half brother. When negotiations were unsuccessful, Kirk lead a team to take the hostages back by force leaving Commander Chekov in command.

Kirk and his team were captured by Sybok and his followers, so that Sybok could use the Enterprise for travel to a planet in Vulcan religion called Sha Ka Ree located in the center of the galaxy. Sybok was killed by the entity claiming to be God, and Kirk regained control of the Enterprise.

The final mission for the Enterprise-A came in 2293 when the Klingon moon Praxis exploded, which crippled the Klingon Empire and opened up a major peace initiative. The Enterprise was sent to escort the Klingon flagship, the K'T'inga-class IKS Qo'noS One to Earth. The Qo'noS One was attacked by a cloaked Bird-of-Prey making it look like the Enterprise was responsible, while two Starfleet assassinated Chancellor Gorkon. When

Captain Kirk and Doctor McCoy beamed over to the Qo'noS One they were held responsible for the attack and were sentenced life imprisonment on Rura Penthe. Once Kirk and McCoy were rescued by the Enterprise, they headed for Khitomer, and with the assistance of Captain Sulu of the USS Excelsior NCC-2000 they destroyed the prototype Bird-of-Prey and saved the peace talks from conspirators in both the Federation and Klingon governments.

The Enterprise-A was retired after the mission with only a lifetime of seven years.

Star Trek Encyclopedia background information
Gene Roddenberry reportedly suggested that the Enterprise-A had been previously named the Yorktown, since it seems unlikely that Starfleet could have built an all-new ship so quickly. Also this would explain why the ship was retired so soon into its service.