Northrop Tacit Blue

The Northrop Tacit Blue was a highly classified experimental aircraft developed by Northrop in the early 1990s to demonstrate low‑observable, or stealth, radar‑cross‑section reduction for airborne platforms. Initiated in 1989 under the codename 'RFI' (Radar Frequency Interceptor), the program produced a twin‑engine, mid‑wing design that first flew in 1991 at Area 51. Although it never entered production, Tacit Blue proved that shaping, radar‑absorbent materials, and an internal weapons bay could together lower an aircraft’s radar signature to a level previously thought impossible for a non‑fighter vehicle.

Key features included a faceted fuselage reminiscent of the later B‑2 bomber, extensive use of composite skins laced with iron‑based ferrite particles, and a sophisticated flight‑control system that maintained stability despite the unconventional geometry. The aircraft also carried a suite of sensors to test the performance of low‑observable avionics in a realistic environment.

Tacit Blue’s significance lies in its role as the technological bridge between the F‑117 and the B‑2, providing critical data that shaped modern stealth concepts. Its legacy endures in today’s low‑observable aircraft, unmanned systems, and the broader understanding of radar‑signature management.