Aviation squadron

United States

Also in contrast to USAF flying squadrons, most tactical sea-based and land-based U.S. Naval Aviation squadrons (USN and USMC), vice training squadrons and test and evaluation squadrons, usually do not have more than 12 aircraft authorized/assigned at any one time. Exceptions are USN helicopter mine countermeasures squadrons (17 MH-53), USMC "composite" medium tilt-rotor squadrons assigned afloat as the Aviation Combat Element (ACE) of a Marine Expeditionary Unit (MEU), (12 MV-22s, 6 AH-1s, 4 CH-53s, 3 UH-1s, and 6 AV-8s). Other squadrons with a large number of Primary Aircraft Assigned (PAA) include Marine heavy helicopter squadrons (16 CH-53s), Marine light/attack helicopter squadrons (18 AH-1s and 9 UH-1s), and Marine attack squadrons (16 AV-8s).