The ship was lost on her third mission, in the Delta Triangle, several decades before 2269. The ship encountered a time warp vortex and became trapped inside Elysia, a small alternate universe, a parallel time continuum, that periodically touched the prime universe in the Delta Triangle region. In Elysia, the Bonaventure remained adrift along with a large number of other ships unable to escape.
Background information Edit
The Bonaventure might have been named after the Bonaventure (C1-21). There have also been several ships in the Royal Navy with the name HMS Bonaventure. The Royal Navy aircraft carrier HMS Powerful was renamed HMCS Bonaventure by the Royal Canadian Navy in 1952.
Star Trek: Star Charts (p. 64), named the ship as SS Bonaventure and listed the year it was lost in the Delta Triangle, over 200 light years away from Earth, as 2079. This date would be consistent with the fact that a Human female was a member of the Elysian Council where everyone was stated to be several centuries old. The Bonaventure's 23rd century design features are however somewhat inconsistent with the early 21st century Earth starship design, as it was later on depicted in Star Trek: Enterprise.
The earlier reference book Star Trek Spaceflight Chronology also featured information on the Bonaventure. According to the book, the UNSS Bonaventure was a warp 2.5 cruiser of the Cochrane class under the command of Captain Hadrian Huckleby. The ship was Earth's first warp drive ship and began Earth's warp drive era with a trip to Tau Ceti four years after the first successful demonstration of warp technology. The ship was unaccountably lost on her third mission, eighteen years later, on the voyage to Sirius. The UNSS Bonaventure was stated to have a maximum emergency velocity of warp 2.5, although engines experienced a slight power breakdown at that speed. The Bonaventure was also the first Earth ship to use alien technology as the warp guidance system. The design of the ship depicted in the book was, however, completely different from what was seen in "The Time Trap" and a starship going beyond warp factor 2 this early is inconsistent with what was later on established in ENT: "First Flight".
The undeveloped Star Trek: The First Adventure movie was to feature the first dilithium-powered warp test ships in the 23rd century, called the Bonaventure and Bonaventure II, a new technology Montgomery Scott and George Kirk worked on. However, if the Bonaventure was truly the first starship from Earth with warp drive, the ship would have had to be launched before the SS Valiant was launched in 2065 and after the launch of the Phoenix in 2063.