The USAF took delivery of the O-2 Skymaster in March 1967 and the O-2A also entered the U.S. Army's inventory during 1967, from USAF stock. By 1970, a total of 532 O-2s had been built, in two variants, for the USAF.
During the Vietnam War, the O-2A was introduced as a replacement for the O-1 Bird Dog, in the forward air control (FAC) aircraft and served in that role with the 20th Tactical Air Support Squadron. The O-2B was equipped with loudspeakers and a leaflet dispenser for use in the psychological operations (PSYOPS) role.
While it was intended that the Skymaster be replaced in the FAC mission by the OV-10 Bronco, the O-2A continued to be used for night missions after the OV-10's introduction, due to the OV-10's high level of cockpit illumination, rendering night reconnaissance impractical.The O-2 was phased out completely after additional night upgrades to the OV-10.
A total of 178 USAF O-2 Skymasters were lost in the Vietnam War, to all causes.