A squadron in air force, army aviation, or naval aviation is 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, cargo aircraft, or air refueling tankers have around 12 aircraft as a typical authorization, while most land-based fighter equipped units have an authorized number of 18 to 24 aircraft.
In naval aviation, sea-based and land-based squadrons will typically have smaller numbers of aircraft, ranging from as low as four for early warning to as high as 12 for fighter/attack.
In most armed forces, two or more squadrons will form a group or a wing. Some air forces (including the United States Air Force, Royal Netherlands Air Force, Belgian Air Component, German Air Force, Republic of Singapore Air Force) also use the term "squadron" for non-flying ground units (e.g., radar squadrons, missile squadrons, aircraft maintenance squadrons, security forces squadrons, civil engineering squadrons, range operations squadrons, range management squadrons, weather squadrons, medical squadrons, etc.).