Canon facts Backstage Info  Speculation

Notes : The history of the Excelsior class tends to consist of extremes. Initially fitted with a Transwarp drive and proclaimed "the great experiment", the ship had an ignoble start when its engines failed when it was called into action to prevent the theft of the USS Enterprise. Although this was due to deliberate sabotage, it transpired that the Excelsior had been saved from a major disaster; engineers working to correct the damage discovered a series of flaws in the Transwarp drive which, had it been used, would have caused a nacelle implosion which would have destroyed the ship. The Excelsior spent nearly a full year in Spacedock while engineering specialists struggled to repair the problem. Re-launched early in 2286, the ship met with little more success. Although the fatal flaw of the Transwarp drive was repaired, the system was subject to major problems and over the next year it never completed a successful test, much to the embarrassment of Captain Styles and his crew. Finally Starfleet cancelled the Transwarp project altogether, and for a short time the Excelsior faced decommissioning. There was nothing wrong with the basic engineering of the space frame however, and in all other areas the Excelsior class was still the most advanced ship in Starfleet, and indeed the entire Quadrant, by a considerable margin.In light of this Starfleet rapidly decided to fit the Excelsior class with a more conventional propulsion system. She returned to Spacedock for the third time in 2287 to have her hull converted to run with a standard Warp drive. This process went remarkably smoothly, and by the end of the year the Excelsior was in space again. From here the history of the ship leapt from one extreme to the other; from being a costly and embarrassing failure, the Excelsior rapidly built a reputation for outstanding performance and a solid reliability few other designs have matched. Series production commenced at once, and continued unbroken for the next thirty nine years - a record for Federation shipbuilding.The Excelsior herself was assigned to Captain Sulu in 2290 and conducted extensive scientific, exploratory and diplomatic missions under his distinguished command. Today the ships of the Excelsior class continue in service, having undergone many refits and upgrades over the decades.