How long a 40-knot Southampton-New York crossing would take

How long would a ship averaging 40 knots take to sail directly from Southampton to New York?

Roughly four days and fourteen hours, using R34's transatlantic passage as a historical comparison for the time and average speed.

The panel estimates that a ship maintaining a forty-knot average between Southampton and New York would complete the crossing in about four days and fourteen hours. It uses the airship R34's transatlantic voyage as a rough historical comparison because its elapsed time and average speed fall near the proposed case. The answer also shows why an average passage speed is more useful than a vessel's headline maximum speed. For transport planning, the entire route must be sustained at the assumed pace rather than reached only briefly during trials.