The U.S. Navy wants to decommission its oldest aircraft carrier, the USS Enterprise (CVN 65) three years early, in 2012. Originally, the Enterprise was going to stay in service until the USS Ford entered service in 2015. But changes in aircraft weaponry, namely smart bombs and targeting pods, have reduced the need for eleven carriers. The navy believes ten will get the job done. Plus, the Enterprise, as the world's first nuclear powered carrier, will also be the first to be decommissioned. That will mean removing eight nuclear reactors. Unlike later nuclear carriers, which had only two reactors, the Enterprise was designed so that one reactor replaced one of the steam boilers of a non-nuclear power plant. The navy had decommissioned nuclear powered surface ships before, having retired nine nuclear powered cruisers in the 1990s. This was done because these ships were more expensive to operate and upgrade.
The Enterprise was an expensive design, and only one was built (instead of a class of six). While a bit longer than the later Nimitz class, it was lighter (92,000 tons displacement, versus 100,000 tons). The Enterprise was commissioned in 1961, almost 40 years after the Langley entered service (1923). In the two decades after the Langley, the first U.S. carrier, went to sea, there were tremendous changes in carrier aviation. While the innovation slowed after World War II, major changes continued into the 1950s (jet aircraft, nuclear propelled carriers, SAMs). But in the ensuing half century there has been no particular innovation in carrier design. This has not been a problem because the carriers have proven useful, at least for the U.S. Navy (the only fleet to use large carriers.) Only the U.S. has a constant need to get air power to any corner of the planet in a hurry. But no navy has been able to give battle to the U.S. carrier force since 1945. The Soviets built new weapons and made plans to do so, but that war never occurred. Many naval planners worry that the next war will find carriers coming off second best to nuclear submarines and missiles. As in the past, we'll never know unless there's a war to test any new theories about how you give battle to aircraft carriers.
Smart bombs, shipboard automation, computer networks, UAVs and major advances in electronics have created another burst of change for carriers. The USS Ford will incorporate many of those innovations. But the biggest change was the predictable precision of the JDAM (GPS guided bomb). Unlike dumb (unguided) bombs, JDAM can hit the target in any weather. Even in clear weather, it would take over 100 dumb bombs to obtain the same effect. This is a big deal for a carrier, which only has a few dozen bomber aircraft, and limited quantities of jet fuel and bombs. But with one F-18 now able to do the work of a hundred, carriers suddenly became far more powerful. Thus the navy would rather save some money, and retire the Enterprise early. The Nimitz, due to retire in 2024, might also be stricken five or more years early. The navy knows it needs more money for new tech, like combat UAVs operating from carriers. These are smaller and burn less fuel than manned fighter-bombers, further increasing the combat capabilities of existing carriers.