VC-137A 58-6970, 58-6971, 58-6972, re-deseginated VC-137B after re-engining, C-137B following removal from VIP role
Thanks, they were fairly common visitors at Heathrow in the 70s/80s and I was trying to recall yesterday if they were VC-135s or VC-137s.
Looking at ADSB, some of the RC-135s visiting the UK have interesting designations and missions, one I noticed recently was an RC-135S Cobra Ball - can't recall if it was an overflight or heading into Mildenhall.