Many design issues came to mind.  What type of landing gear would work best?  What aerodynamic shape should he use?  Which airfoil would be most effective?  Before he made those decisions, however, he needed to know just how far the plane would fly as it crossed the Atlantic.  Using a piece of string, they measured a distance of 3,600 miles from New York to Paris.  Rounding the figure to 4,000 provided a fuel reserve for potential navigational corrections.  A flight of 4,000 miles would require 400 gallons of fuel. Although the M-2 tail surfaces and wing ribs would be incorporated into the final design, saving valuable time.