Airman: (single Air Force member)
Section: Two or more airmen can form a "section." Generally, the section is the place (duty section) where the person works. For example, the Administrative Section, or the Life Support Section. It's not absolutely necessary to have a "section." For example, many aircrew members and Security Forces (Air Force "cops") don't have a "section." Instead, they belong (as a group) to a "flight." In Air Force Basic Training, it's called an "Element." Each basic training "flight" is divided into four "elements," each with an assigned "element leader."
Flight: Two or more airmen can form a flight. Two or more sections can also form a flight. It depends upon how the Squadron is organized. There are three types of flights: Numbered, Alpha, and Functional. Numbered flights incorporate small mission elements into an organized unit. For example, flights in basic training are numbered flights. While in basic, you could be assigned to "Flight 421," for instance.
Alpha flights are components of a squadron and consist of elements with identical missions. Flights A, B, and C, of a Security Forces Squadron would be an example, or A, B, C of an F-16 Fighter Squadron.
Functional flights consist of elements with specific missions. The "Military Personnel Flight (MPF)" and the "Social Actions Flight" are two examples of functional flights.
Squadron: Two or more flights form a squadron. The squadron is the lowest level of command with a headquarters element (example, a Squadron Commander, or Squadron First Sergeant). In the Air Force, a squadron commander is generally in the rank of Lt Col (O-5), although smaller squadrons may be commanded by majors, captains, and sometimes even lieutenants. Squadrons are usually identified both numerically, and by function. An example would be the 49th Security Forces Squadron, or the 501st Maintenance Squadron.
Group: Two or more Squadrons form a Group. In the Air Force, Groups are usually based upon assignment of squadrons with similar functions. For example, the Supply Squadron, Transportation, and Aircraft Maintenance Squadron would be assigned to the Logistics Group. The flying squadrons would be assigned to the Operations Group. The Dental Squadron and the Medical Squadron would be assigned to the Medical Group, etc. Usually, Groups take on the number of the Wing they are assigned to. The 49th Logistics Group, for example is assigned to the 49th Fighter Wing, at Holloman AFB in New Mexico. The group commander is usually a colonel (O-6).
Wing: Two or more groups compose a Wing. There is only one Wing on an Air Force base, and the Wing Commander is quite often considered to be the "Installation Commander." There are two types of Wings: Composite and Objective.
Composite Wings operate more than one kind of aircraft. Individual composite wings can have different missions.