By the mid 1970 until the end of 1971 General Dynamics built three RC 135 c to the RC-135U combat sent for special electronic reconnaissance by the big Safari program. They belong to the externally visible variants of the RC-135 series. The RC-135U wear but not the big nose, but a radome under the nose, front-facing, an another a few meters behind, large panels on the sides of the bow, to multiple dipole antennas, extended wing ends with antennas and a rear fairing with sensors. With spectrometers, interferometers, radiometers, signals from radar and other sources can be traced and examined.
Combat sent 63-9792 rebuilt the strategic air command in 1976 in a RC-135V, the other two (64-14847 - 14849) today and are in service at the 55th strategic reconnaissance wing of the Offutt AFB.