The 104th Fighter Squadron (104th FS), nicknamed the Fightin' O's, is a unit of the Maryland Air National Guard 175th Wing stationed at Warfield Air National Guard Base, Middle River, Maryland. The 104th is equipped with the Fairchild Republic A-10C Thunderbolt II. The squadron is a descendant organization of the 104th Squadron (Observation), which was formed on 29 June 1921. It is one of the 29 original National Guard Observation Squadrons of the United States Army National Guard formed before World War II and is the oldest unit of the Maryland Air National Guard.