Source: American Geographical Society Library, University of Wisconsin-Milwaukee Libraries.
The great circle distance between New York and Paris is about 3,600 miles. The first time the great circle distance was practically used for air travel was in 1927, when Lindbergh plotted his transatlantic flight through a series of continuous segments with correction points at defined distances. Actually, Lindbergh used two map projections to plan his route and navigate across the Atlantic. One was the standard Mercator projection, where longitudes and latitudes are straight lines, which is helpful for navigation (clear north/south and east/west orientation). The other was a gnomonic projection centered along the Atlantic that showed the path between New York and Paris as a straight line composed of points 100 miles apart.
From this projection, Lindbergh transferred each point from that line to the Mercator projection, which became a curved course connecting New York and Paris (see the above map depicting a simplification of the route at 500-mile intervals from New York). At each point, Lindbergh marked the distance from New York, and determined the course adjustment. Each point also accounted for the variation to the magnetic north as one traveled across the Atlantic. After 33 hours and 30 minutes of non-stop flight, Lindbergh arrived at his set destination with limited navigation errors. Most modern transatlantic flights between New York and Paris follow a similar path.