may be flying units composed of pilots and flight crews, with designations such as fighter squadron, bomb squadron, or airlift squadron. Fighter squadrons may support between 18 and 24 aircraft, while larger aircraft flying squadrons (e.g., bomber, cargo, reconnaissance) may support fewer aircraft. However, non-flying units also exist at the squadron level, such as missile squadrons, aircraft maintenance squadrons, intelligence squadrons, aerospace medicine squadrons, security forces squadrons, civil engineering squadrons and force support squadrons, as well as numerous other examples. USAF flying squadrons are typically commanded by an aeronautically rated officer in the rank of lieutenant colonel, although some particularly large squadrons, such as the 414th Combat Training Squadron that manages RED FLAG training at Nellis AFB, Nevada will be commanded by an aeronautically rated officer in the rank of full colonel. Non-flying squadrons are also usually commanded by an officer in the rank of lieutenant colonel, but some may also be commanded by officers in the rank of major. In contrast to the organizational structure of United States Air Force units, where flying squadrons are separate from non-flying squadrons tasked with administrative, aircraft maintenance, or other support functions, flying squadrons in naval aviation in the United States (e.g., United States Navy and United States Marine Corps) typically contain both embedded administrative support functions and organizational level aircraft maintenance functions, plus all their associated personnel, as part of the total squadron manning. With few exceptions, oversight of the majority of these non-flying functions is assigned to the squadron's naval aviators and naval flight officers as their "ground job" in addition to their regular flying duties. With few exceptions, most U.S. Navy flying squadrons are commanded by aeronautically designated officers in the rank of commander. Exceptions are primarily the Fleet Replacement Squadrons (FRS), which are often, though not always, commanded by aeronautically designated captains. Commanding officers (COs) of U.S. Navy flying squadrons other than FRS units will be assisted by an Executive Officer (XO) of the same rank who functions as a second-in-command and who will eventually "fleet up" and relieve the CO as the next CO. In United States Marine Corps Aviation, in addition to flying units that are patterned in similar fashion to their U.S. Navy counterparts, the nomenclature "squadron" in the Marine Corps is also used to designate all battalion-equivalent, aviation support organizations. These squadrons include: wing headquarters, tactical air command, air control, air support, aviation logistics, wing