The Delta Flyer was the name given to a ship other than that attached to USS Voyager for the purposes of deception.
In 2376, three con artists known as Dala, Mobar, and Zar impersonated Kathryn Janeway, Tuvok, and Chakotay respectively. In their ruse, they called their ship the Delta Flyer after the Delta Flyer attached to the USS Voyager – claiming that its dilapidated condition was due to it having been through so much – and used Voyager's story to steal from others and sell meaningless memberships to the Federation. Eventually, the real Voyager caught up to the ship and its occupants.(VOY: "Live Fast and Prosper")