The USMC employs sections as intermediate tactical echelons in infantry, armored vehicle units (individual vehicles being the base tactical element), and low altitude air defense (LAAD) units, and as the base tactical element in artillery units. Infantry sections can consist of as few as eight Marines (heavy machinegun section) to as many as 32 in an 81-mm mortar section. In headquarters, service, and support units throughout the USMC (CE, GCE, ACE, and LCE), sections are used as functional sub-units of headquarters or platoons. For example, the intelligence section (S-2) of a battalion or squadron headquarters; the communications-electronics maintenance section, communication platoon, regimental headquarters company; armory section, Marine aviation logistics squadron. In Marine aircraft squadrons, section is also used to designate a flight of two or three aircraft under the command of a designated section leader. Some sections, such as weapons platoon sections are led by a staff non-commissioned Officer (SNCO), usually a staff sergeant. Tank and other armored vehicle sections, as well as service and support sections, may be led by either an officer, usually a lieutenant (or a CWO, in the case of service and support units), or a SNCO ranging from staff sergeant to master sergeant. Headquarters and aircraft sections are always led by a commissioned officer. Rifle squads generally contain 13 marines.