Beginning on February 13, 1926, the U.S. Post Office issued three airmail stamps with a new design to satisfy the new airmail postage rates. Each stamp depicting two bi-planes superimposed over a topographical map of the United States which was provided by the U.S. Geological Survey of the Department of the Interior, showing the rivers and mountain ranges that were used by pilots to navigate their way across the country. Along with paying various postage rates for airmail delivery the new stamps were also valid for regular mail delivery. On February 15 the new contract airmail service began. To help postal clerks sort letters, the Bureau of Printing and Engraving designed the stamps in a new format, each with their own distinctive color. The 10-cent blue stamp paid the air postage on one ounce letters mailed to destinations up to 1,000 miles (referred to as the first zone, etc); the 15-cent brown stamp for destinations up to 1,500 miles; the 20-cent yellow-green for destinations over 1,500 miles. On each side of the central image was a de Havilland DH-4 single-engine biplane in flight, one traveling west and one east. This particular plane had also served as a bomber and reconnaissance airplane during World War I. After the war, the U.S. Government and Post Office purchased one hundred of these planes for use in airmail delivery service.^[1]