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". In earlier times, especially in British usage, the ships were said to be "laid up in ordinary".
A reserve fleet may be colloquially referred to as a "ghost fleet".[1] In the 21st century, ghost fleet may also refer to an active shadow fleet of aged reserve fleet oil tankers returned to an active service in order to circumvent commodities sanctions.[2][3][4]