Aft also describes the direction of movement within an aircraft; that is, towards the tail. Example: "Let's go aft." It may also describe the back/tail location or region within an aircraft cabin. Example: "Aft lavatory."
The difference of aft and stern is that aft is the inside (onboard) rearmost part of the vessel, while stern refers to the outside (offboard) rearmost part of the vessel.