Alpha Nine was the designation for a ship used by the Maquis in a joint attack of a Cardassian convoy in 2370.
Kalita piloted this ship during the Maquis attack. After the convoy was revealed to be a trap, planned by Starfleet to neutralize Maquis resistance, Lieutenant Ro Laren defected to the Maquis, and Alpha Nine retreated to safety with the rest of the fleet. (TNG: "Preemptive Strike")
Alpha Nine was never seen on screen.