 LeMay used the Rex's noon position report of 11 May in conjunction with known routes and speeds of ocean liners bound for New York to calculate an intercept point for the next day, based on the ship's expected noon position for 12 May. An updated position report to refine his calculations was expected that evening but not received. Weather conditions deteriorated during the night, with a forecast that "ceilings would be down to nothing" in the vicinity of the anticipated interception.
