Clipper One as I recall was Pan Am's east-bound round the world flight and Clipper Two was west bound. Is that right?
BEA were Bealine, not remit of the question though.
Military Airlift Command used to be MAC followed by the aircraft's FY serial, though I gather if, say, C-5 70-0446 had gone tits up on the ramp, and 70-0457 flew the mission, the flight planned serial was used! My teenage spotter's logbook was a tissue of lies folks...