The U.S. Navy has disbanded one of its ten Carrier Strike Groups (SCGs), leaving only nine of them for the eleven aircraft carriers in service. This is a money saving measure, as nuclear powered aircraft (CVN) carriers spend twenty percent of their time out-of-service having maintenance done. Thus only 8-9 CSGs are needed at any one time.
The SCG is actually a complex organization. There is the CVN and its crew, and the CAW (Carrier Air Wing), which includes all the aircraft, pilots and support personnel. The CAWs do not stay with the same CVN, but move around. When a CVN goes in for maintenance, its CAW will move ashore and then to another carrier (usually one coming out of dry dock). Also part of a SCG are the escort ships (usually a destroyer squadron of 2-4 destroyers, cruisers or frigates) and one or two SSNs (nuclear attack subs). There is also one or two supply ships (carrying spare parts and maintenance personnel for all ships, as well as fuel for the escort ships.)
Until a few years ago, the U.S. had twelve carriers, but new ones are not being built quickly enough to replace the older ones that must retire (because of old age). Soon there will only be nine CVNs, and there will be cost cutting pressure to disband another SCG.