Pilot Lt Col Erik C Swanson (ret.) concludes his description of serving on the KC-135Q force supporting the SR-71A Blackbird on its secret missions
When the SR-71 flew from Mildenhall, five tankers were used, with one tanker acting as a manned ground spare, ready to take-off and assume the refuelling duties of any of the four primary tankers in case of a mechanical malfunction or emergency. The first tanker took off about 30min before the SR-71 departed. For the more sensitive missions the SR-71 and the supporting KC-135Qs would depart under radio-silent procedures getting take-off clearance via a green light from the air traffic control tower.