OVERVIEW: The RC‑135U Combat Sent is a strategic ELINT reconnaissance aircraft operated by the U.S. Air Force. As of 2020, it is undergoing extensive Baseline 6 upgrades to enhance radar emitter collection and processing capabilities.

DETAILS: Developed under Project Big Safari by converting RC‑135C airframes in 1970–71, the Combat Sent entered service in 1971 with the 55th Wing at Offutt AFB. It is powered by four CFM F108‑CF‑201 turbofan engines, with a cruise speed of ~850 km/h (Mach 0.66), ceiling of ~12,800 m, and a range of ~6,500 km without refuelling. The airframe features chin and wingtip antenna arrays, large cheek fairings, and an extended tail housing advanced ELINT suites. Staffing includes two pilots, one navigator, two systems engineers, ten EW officers, and additional mission specialists.

Baseline 6 upgrades, initiated in FY2020, add wideband collection, advanced ELINT and MASINT processors, improved antennas, enhanced operator interfaces, and integration of the RC‑135W Rivet Joint COMINT suite, along with support for dense signal environments and SATCOM reachback.

TYPE: Strategic ELINT Reconnaissance Aircraft

FUNCTION: The RC‑135U Combat Sent locates, classifies, and collects technical data on foreign radar emitters to support U.S. missile warning systems, EW development, and military readiness. Baseline 6 improvements enhance its operational versatility and data fidelity.

NOTE:
IOC: 1971
Manufacturer: Boeing (airframe); L3Harris/Textron (mission systems)
Operators: U.S. Air Force – 55th Wing (45th RS & 97th IS)
Fleet Size: Two active aircraft
Conflict used in: Cold War radar profiling, Balkans, Middle East, Black Sea intercepts, Asia-Pacific missions

SOURCE:
U.S. Air Force Fact Sheet – RC‑135U Combat Sent: https://www.af.mil/About-Us/Fact-Sheets/Display/Article/104495/rc-135u-combat-sent/ ; Air & Space Forces Magazine: https://www.airandspaceforces.com/weapons-platforms/rc-135u/ ; GlobalSecurity.org – COMBAT SENT overview: https://www.globalsecurity.org/intell/systems/combat_sent.htm ; C‑MANO DB – RC‑135U Baseline 6: https://cmano-db.com/aircraft/5853/ ; FAS – COMBAT SENT upgrades tool: https://irp.fas.org/program/collect/combat_sent.htm