Kitty Hawk-class aircraft carrier
The "Kitty Hawk"-class supercarriers of the United States Navy were an incremental improvement on the vessels. Three were built, all in the 1960s, (1961–2009), (1961–2003), and (1965–1996), as well as the variant (1967–2007). All are now decommissioned. Improved "Forrestal" carriers. The biggest differences from the "Forrestal"s are greater length, and a different placement of elevators; two are forward of the island, one is aft of the island and another on the portside stern. The movement of the No. 4 elevator from the forward to the after end of the angle made it useful for aircraft  movement, since the forward-end elevator in the "Forrestal"s was sited in both the landing path and in the launch path of the waist catapults. Three different shipyards were used to construct the ships. "Kitty Hawk" was built at New York Shipbuilding Corporation, "Constellation" at New York Naval Shipyard, "America" and "John F. Kennedy" at Newport News Shipbuilding. "John F. Kennedy" is similar to the earlier units in flightdeck arrangement and propulsion, but has enough differences that she is placed in her own class. Propulsion consisted of four Westinghouse geared turbines, , four shafts with eight Foster Wheeler boilers. Construction and  design differences. The initial design for the class was known as SCB 127, and "Kitty Hawk" and "Constellation" were completed to design SCB 127A. The first three units were constructed with a Terrier surface-to-air missile system. The supporting missile launchers and AN/SPG-55 radars consumed a large amount of space, while at the same time duplicating the capabilities of the air defence escorts, and were later removed. "John F. Kennedy" did not have Terrier and was built with the shorter ranged Sea Sparrow, Basic Point Defense Missile System (BPDMS). All were eventually equipped with NATO Sea Sparrow (NSSM ) and Phalanx CIWS for self-defense. In 2001, "Kitty Hawk" received two Rolling Airframe Missile launchers replacing the forward Sea Sparrow and Phalanx CIWS equipment. The SLQ-32 Electronic Warfare Suite was added as part of the Service Life Extension Program (SLEP) on "Kitty Hawk" and "Constellation". "America" was designed under project SCB 127B and so had several differences from the lead units of the class. Instead of two forward anchors, one on each side, "America" had no port side anchor and an additional anchor astern, a change made to accommodate the AN/SQS-23 sonar. "America" was the only post-World  War II U.S. carrier to be built with sonar, which was however removed in the early 1980s. She also had a narrow smokestack compared to prior units. Section::::"John F. Kennedy" class. was originally scheduled to be the fourth "Kitty Hawk"-class carrier, but because she received so many modifications under project SCB 127C, she formed her own ship class and is often listed as a single-vessel class. "Kennedy" had similar design changes regarding the anchors to accommodate a sonar array, but the sonar was never installed. There was also a proposal to make her nuclear powered under competing project SCB  211A, but since Congress would not authorize it, "Kennedy" was constructed as a conventionally powered carrier. Her smokestack is also different and tilts outboard to send stack gas away from the flight deck. The angled end of the waist is also different from the other "Kitty Hawk"s, bearing a closer resemblance to that of the . "Kennedy" is also shorter in length than the other "Kitty Hawk"-class carriers. Decommissioning. From 1987 to 1991 "Kitty Hawk" was overhauled for $785 million under the Service Life Extension Program (SLEP) at Philadelphia Naval Shipyard. From 1990 to 1992, "Constellation" received her $800  million service life extension also in Philadelphia. The program was intended to add 15 years to the life of the ships. "John F. Kennedy" was not overhauled as part of SLEP. Instead, from 1993 to 1995, she received a $491 million overhaul. It was the final project of Philadelphia Naval Shipyard prior to its closing. "America" had been scheduled to be overhauled under the service life extension program after "Constellation", but she was decommissioned 9 August 1996 instead, during a time of budget cuts after the Cold War. "America" was in very poor condition when she was decommissioned, and  therefore despite her historical significance was not held as a donation asset. She was expended as a live-fire target and sunk on 14 May 2005. "Constellation" was decommissioned 7 August 2003. "John F. Kennedy" was decommissioned on 23 March 2007. Only "Kitty Hawk" remained in service as of early 2008 and was replaced by as the forward-deployed carrier in Japan. "Kitty Hawk" returned to the United States after the turnover. She was decommissioned on 12 May 2009.