The Austerlitz class was a proposed class of Tau'ri spaceship designed by Ariane during the period that Atlantis had returned to Earth. Construction was halted on the class due to financial issues, however, and so it remained on the drawing board. (SGA: "Legacy: Homecoming")
Work was resumed sometime after Atlantis returned to the Pegasus galaxy, though only a single hull of this class was laid down by the EU who would operate it once completed. (SGA: "The Furies")