A squadron in air force, army aviation, or naval aviation is mainly a unit comprising a number of military aircraft and their aircrews, usually of the same type, typically with 12 to 24 aircraft, sometimes divided into three or four flights, depending on aircraft type and air force. Land based squadrons equipped with heavier type aircraft such as long-range bombers, or cargo aircraft, or air refueling tankers have around 12 aircraft as a typical authorization, while most fighter equipped units have an authorized number of 18 to 24.
In most armed forces, two or more squadrons will form a group or a wing. Some air forces (including the Royal Air Force, Royal Netherlands Air Force, Belgian Air Component, German Air Force, Republic of Singapore Air Force, and United States Air Force) also use the term squadrons for non-flying ground units (e.g., radar squadrons, missile squadrons, aircraft maintenance squadrons, security forces squadrons, civil engineering squadrons, operations management squadron, medical squadrons, etc.).
In contrast to United States Air Force units where flying squadrons are separate from supporting administrative and aircraft maintenance squadrons, flying squadrons in U.S. Naval Aviation (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.