The V-22B has other variants, such as the CV-22B, developed for the US Air Force. Other variants for the Royal Navy, Anti-submarine Warfare and Search and Rescue have been proposed. The aircraft is manned by a pilot, copilot, and enlisted aircrew appropriate for the specific service and type of mission being flown. The V-22 is optimized to transport troops (i.e., 24 combat-equipped Marines, or 10,000 pounds of external cargo) to austere landing sites from aviation capable amphibious ships and expeditionary forward operating bases ashore. The V-22 would be capable of flying over 2,100 nautical miles with one aerial refueling, giving the Services the advantage of a Vertical/Short Takeoff and Landing aircraft that can rapidly self-deploy to any location in the world.