I've mentioned composite squadrons and detachments before. See http://thanlont.blogspot.com/2012/12/hellcats-on-cves.html for a summary description of WW II composite squadrons and http://thanlont.blogspot.com/2009/11/air-groups-and-markings-in-transition.html for a brief discussion of detachments from a markings standpoint.
These units arose from the need to properly manage much smaller groups of airplanes and people than assigned to the existing squadrons in a carrier air group. For example, the first helicopter deployments aboard carriers typically only involved two aircraft and a handful of personnel. As a result, two helicopter utility squadrons were formed, one (HU-1) based on the west coast and one (HU-2) on the east coast, that supplied detachments to aircraft carriers, cruisers, etc. These were big squadrons from the standpoint of aircraft, naval aviators, and maintainers. (They were reportedly even overstaffed, as some naval aviators were reluctant to transition from props to jets and sought an alternative assignment in the burgeoning need for helicopter pilots.)
HU-1 used the tail code UP:
Similarly, so-called composite squadrons were formed to provide small detachments of specialized mission airplanes (night attack, night fighter, airborne early warning, reconnaissance, etc.) to deploying air groups. These were different in usage from the World War II composite squadrons, which deployed as a unit.
One example is VC-35, which was eventually redesignated VA(AW)-35. As the subsequent designation indicates, it was an all-weather squadron. However, initially it was assigned more missions than simply attack, including ASW, hence the use of C for composite. During the Korean War, it provided detachments to attack carrier air groups deploying from the west coast, flying AD-4Bs, AD-4Ns, and NLs with the squadron tail code NR.
Another example is VFP-62, the east coast photo-reconnaissance squadron. It was assigned tail code GA.
In October 1962, VFP-62 had 29 RF-8As (redesignated from F8U-1P the month before) assigned, 20 of which were deployed with seven detachments. Seven of the remainder were flyable when the squadron was tasked with providing photo-reconnaissance of suspected ballistic missile sites in Cuba with an eighth detachment of eight airplanes. The squadron rose to the occasion and received a Presidential Unit Citation, along with a four-RF-8A VMCJ-2 detachment, personally presented by President Kennedy.