Naval Fleet Auxiliary Force The Naval Fleet Auxiliary Force is a division of the US Navy . The 42 ships of the Military Sealift Command ' s Naval Fleet Auxiliary Force are the supply lines to U . S . Navy ships at sea . These ships provide virtually everything that Navy ships need , including fuel , food , ordnance , spare parts , mail and other supplies . NFAF ships enable the Navy fleet to remain at sea , on station and combat ready for extended periods of time . NFAF ships also conduct towing , rescue and salvage operations or serve as floating medical facilities . All NFAF ships are government owned and crewed by civil service mariners . Some of the ships also have a small contingent of Navy personnel aboard for operations support , supply coordination and helicopter operations . Fleet Replenishment Oilers . Fifteen fleet replenishment oiler s , the largest subset of Naval Fleet Auxiliary Force ships , provide fuel to deployed Navy ships at sea , as well as to their assigned aircraft . Oilers and the ships they refuel sail side by side as fuel hoses are extended across guide wires . Underway replenishment of fuel dramatically extends the time a Navy battle group can remain at sea . The fifteen ships of the oiler fleet are as follows : Ammunition Ships . Ammunition ships supply ordnance to Navy combatants at sea , providing service through a combination of alongside transfers and vertical replenishment lifts via helicopter . The ammunition ships of the Auxiliary Fleet are : Fast Combat Support Ships . MSC ' s four fast combat support ships provide one - stop shopping to the fleet for fuel , ammunition , food and other cargo . These ships are especially valuable because of their speed and ability to carry all the essentials to replenish Navy ships at sea . MSC ' s fast combat support ships , formerly sailor - operated , transferred to MSC for civil service crewing beginning in 2001 . Dry Cargo / Ammunition Ships . The eleven Military Sealift Command " Lewis and Clark " dry cargo / ammunition ships are a new class of ships dedicated to the Naval Fleet Auxiliary Force . These ships are able to deliver ammunition , provisions , stores , spare parts , potable water and petroleum products to the Navy ' s carrier strike group s and other naval forces worldwide . Designed to operate for extended periods at sea , the " Lewis and Clark " - class ships have improved cargo handling equipment that increases efficiency and makes the ships more cost effective to operate and maintain . All the " Lewis and Clark " - class ships are named after great American pioneers . Fourteen ships of this class have been ordered with two still to be delivered . These ships are listed as follows : Ordered but not yet delivered are : Fleet Ocean Tugs . The Military Sealift Command ' s fleet ocean tugs provide the Navy fleet with towing service and can tow Navy vessels as large as battleships . When augmented by Navy divers , fleet ocean tugs assist in the recovery of downed ships and aircraft . In addition , when carrying specialized equipment , the fleet ocean tugs can also perform submarine rescue operations . The Auxiliary fleet ' s tugs are : Rescue and Salvage Ships . The MSC ' s four rescue and salvage ship s recover objects from the sea , tow or debeach stranded vessels and provide firefighting assistance . These ships , like fleet ocean tugs , are able to lift objects as heavy as downed ships and aircraft . The key advantage of these ships is their ability to rapidly deploy divers to conduct rescue and salvage operations . They are identified as follows : Hospital Ships . MSC ' s Naval Fleet Auxiliary Force operates the Navy ' s two hospital ship s each containing 12 operating rooms and up to 1 , 000 beds . The ships are normally kept pierside in reduced operating status , each with a small contingent of MSC civil service mariners and Navy hospital personnel aboard to ensure the ships are ready should they be needed . When called into action , they can get underway in five days with an expanded crew of more than 60 civil service mariners and an expanded medical staff of up to approximately 1 , 200 military medical personnel . The Auxiliary Fleet ' s hospital ships are the :