There are only two Combat Sent aircraft in the US Air Force inventory.
The RC-135U Combat Sent, provides strategic electronic reconnaissance information to the president, secretary of defense, Department of Defense leaders and theater commanders.
All RC-135U aircraft are equipped with an aerial refueling system, giving it an unlimited flying range. Communication equipment includes high frequency, very high frequency, and ultra high frequency radios. The navigation equipment incorporates ground navigation radar, a solid state Doppler system, and an inertial navigation system that merges celestial observations and Global Positioning System data. Although the flight crew stations are similarly configured, the reconnaissance equipment is slightly unique within each airframe.
The aircraft are identified by their distinctive antennae arrays on the "chin" and wing tips, large cheek fairings, and extended tail.
Crew composition includes two pilots, two navigators, two airborne systems engineers, and a minimum of 10 electronic warfare officers, or "Ravens," and six or more electronic, technical, and area specialists.
Canadian Airline Blog
Photo source: US Air Force