Potential of the QT-2 / Q-Star was such that Lockheed produced a refined version for the US Army: The YO-3A. Also based on the Schweizer SGS 2-32 Sail-Plane wings and tail unit, but with wings mounted low on the fuselage, retractable landing gear, upgraded (SLAE) avionics, State-Of-The-Art Sensor (NVAP with LTD) and the Tactical Observer seated forward for better visibility. A 156.5kW IO-360D Continental Engine provided propulsion power. The YO-3A was deployed in Southeast Asia from mid-1969 to late-1971.

It was the first military aircraft to employ an integrated NOD Sensor with a YAG Laser. It also had an Infrared Illuminator for other tactical sensors (INFANT LLTV, NODs, etc). The YO-3A was deployed in Vietnam for more than a year.

It was later operated by the Louisiana Dept of Wildlife & Fisheries (LDWF) and FBI. NASA operated the former 69-18010 as NASA 818 (or similar).

 

One YO-3A is preserved in the Army Aviation Museum at Fort Rucker, Alabama. YO-3A 69-18005 is on display at the Museum of Flight in Seattle, Washington. YO-3A 69-18006 is on display at the Pima Air and Space, Tucson AZ. YO-3A 69-18007 is in storage at the Western Museum of Flight in Torrance, California. As of 2014, YO-3A 69-18010 (NASA 818) is in flyable storage at Armstrong Flight Research Center.