A reserve fleet is a collection of naval vessels of all types that are fully equipped for service but are not currently needed; they are partially or fully decommissioned. A reserve fleet is informally said to be "in mothballs" or "mothballed"; an equivalent expression in unofficial modern US naval usage is "ghost fleet". In earlier times, especially in British usage, the ships were said to be "laid up in ordinary". Overview Such ships are held in reserve against a time when it may be necessary to call them back into service. They are usually tied up in backwater areas near naval bases or shipyards in order to speed the reactivation process. They may be modified for storage during such a period, for instance by having rust-prone areas sealed off or wrapped in plastic or, in the case of sailing warships, the masts removed. While being held in the reserve fleet, ships typically have a minimal crew (known informally as a skeleton crew) to ensure that they stay in somewhat usable condition. For instance, bilge pumps need to be run regularly to reduce corrosion of their steel and to prevent the ships from foundering at their moorings. When a ship is placed into reserve status, the various parts and weapon systems that the ship uses are also placed in a storage facility, so that if the warship is reactivated, the proper spare parts and ammunition are available. Like the ships, however, the stored parts and equipment are prone to fall into disrepair, suffer metal corrosion, and become obsolete. Principal reserve fleets The British Reserve Fleet was a repository for British decommissioned warships from c. 1800 until 1960. The United States National Defense Reserve Fleet (NDRF), consisted of about fifty World War II ships that were moored in Suisun Bay (Suisun Bay Reserve Fleet) near San Francisco since the 1950s or '60s. The fleet included military cargo ships, troopships and tankers. As of mid-2021 there are just two ships anchored in that area. Additional NDRF vessels are moored at the fleet sites at Newport News, Virginia (James River Reserve Fleet); Beaumont, Texas (Beaumont Reserve Fleet); and at designated outported berths. Alternatives In practice most reserve ships rapidly become obsolete and are scrapped, used for experiments or target practice, sold to other nations (and occasionally to private companies for civilian conversion), or become museum ships or artificial reefs. Alternatives to reserve fleets include