Originally Posted by
chevvron
'Clipper One' was Pan Am's flagship flight; it was a 'round the world' service eastbound(I think) from the USA; 'Clipper Two' was the opposite direction equivalent.
Clipper 1 was the westbound service, in line with Pan Am's system, which had odd numbers for all westbound flights. On a slightly related point, I recall being in the USA and hearing Pan Am Express Dash 7s and ATR-42s using "Pan Am" as their callsign.