group to have no subordinate squadrons, but merely be a larger unit than a squadron. In such cases the group would not have a headquarters. USAF groups may be dependent or independent: "A dependent group is a mission, maintenance, mission support, medical, or large functional unit (e.g., security forces, special tactics, communications, etc.) that encompasses a number of related squadrons to provide the specified capability to a parent wing. Such groups may possess small supporting staff elements, such as standardization and evaluation or quality control, that are organized as sections." "An independent group has the same functions and responsibilities as a like-type wing but its scope and size do not warrant wing-level designation and associated overhead costs." A group requires at least 400 personnel, while a wing requires at least 1,000. A fighter wing, for example, is normally composed of dependent groups: an operations group of typically three flying squadrons and an operations support squadron and a maintenance group with aircraft, equipment, and component maintenance squadrons and a maintenance support squadron. Wings responsible for an air base also have other dependent groups such as a mission support group (security, communications, logistics support, mission support, and civil engineering squadrons) and a medical group. The dependent group commanders are considered to be in command billets, but they function like staff officers (the A3/S-3/G-3/J3 or the A4/S-4/G-4/J4) in other organizations. Independent groups are effectively small wings with both flying and maintenance squadrons. USAF groups are usually commanded by officers in the grade of OF-5 (US pay grade O-6), i.e., a full colonel. Wings are also usually commanded by officers in the grade of OF-5, but these are typically more senior colonels by virtue of time in grade and/or date of rank. Some USAF wings are also commanded by officers in the grade of OF-6 (US pay grade O-7), i.e., a brigadier general. US Marine Corps Aviation In the United States Marine Corps, a Marine Aircraft Group (MAG), Marine Air Control Group (MACG) or Marine Aviation Training Support Group (MATSG) is a regimental-level unit within United States Marine Corps Aviation, equivalent to a USAF wing. A MAG consists of at least two air aircraft squadrons and two aviation support squadrons; two or more MAGs and a MACG form a Marine Aircraft Wing (MAW). Marine Aircraft Groups consist of two or more aircraft squadrons (usually four to six) and can range to as many as