The Bonaventure was lost in the year 2079, on her third mission. At the time, it was believed that it had suffered a failure due to a design flaw in its warp engines. Cochrane disputed this theory, and the loss of the Bonaventure pushed him to establish the Warp Five Complex. (SCE eBook: Where Time Stands Still) In 2269, the USS Enterprise discovered the Bonaventure trapped inside a "pocket dimension" called Elysia in a region known as the Delta Triangle, in which ships have been mysteriously dissapearing for centuries, being transported to Elysia. (TAS episode: "The Time Trap")