The United States Navy

The Navy operates 290 ships, 3,700 aircraft, 50,000 non-combat vehicles and owns 75,200 buildings on 3,300,000 acres (13,400 km2). The Navy plans to slash the dependence on fossil fuels.
• Ships
The names of commissioned ships of the U.S. Navy are prefixed with the letters "USS", designating "United States Ship". Non-commissioned, civilian-manned vessels of the Navy have names that begin with "USNS", standing for "United States Naval Ship" The names of ships are officially selected by the Secretary of the Navy, often to honor important people or places. Additionally, each ship is given a letter-based hull classification symbol (for example, CVN or DDG) to indicate the vessel's type and number. All ships in the Navy inventory are placed in the Naval Vessel Register, which tracks data such as the current status of a ship, the date of its commissioning, and the date of its decommissioning. Vessels that are removed from the register prior to disposal are said to be stricken from the register. The Navy also maintains a reserve fleet of inactive vessels that are maintained for reactivation in times of need.
The U.S. Navy was one of the first to install nuclear reactors aboard naval vessels; today, nuclear energy powers all of U.S. active aircraft carriers and submarines. In the case of the Nimitz-class carrier, two naval reactors give the ship almost unlimited range and provide enough electrical energy to power a city of 100,000 people. The U.S. Navy previously operated nuclear-powered cruisers and destroyers, but all have been decommissioned.