Tacit Blue featured a straight tapered wing with a Vee tail mounted on an oversized fuselage with a curved shape. The aircraft has a wingspan of 48.2 feet and a length of 55.8 feet and weighed 30,000 pounds. A single flush inlet on the top of the fuselage provided air to two high-bypass turbofan engines. Tacit Blue employed a quadruply redundant, digital fly by wire flight control system to help stabilize the aircraft about the longitudinal and directional axes.
The aircraft made its first flight in February 1982, and subsequently logged 135 flights over a three year period. The aircraft often flew three to four flights weekly and several times flew more than once a day. The aircraft had been in storage since 1985, and is now on display at the US Air Force Museum at WPAFB, OH.
TACIT BLUE was developed as a potential platform for radar sensors developed under the Air Force Pave Mover and Army SOTAS programs. In 1982, the Undersecretary of Defense for Research and Engineering (USDRE) combined the SOTAS and Pave Mover efforts into a joint program, later designated Joint STARS. From 1982-1984, the services, OSD, and Congress wrestled over the development of requirements for the joint program, as well as the appropriate platform for the sensor. At the time, one option under active consideration was a two-phased program in which the radar would initially be deployed on ten conventional aircraft, with subsequent production focused on a stealth platform derived from the TACIT BLUE test aircraft. In May 1984, the Chiefs of Staff of the Air Force and Army made the final decision to put the Joint STARS radar on a 707 platform.