The De Havilland DH-4 was was the only US built aircraft to see combat during World War I. Only a few arrived at the front before war's end. They were used as bombers and scout planes and were known as "Liberty Planes". The several thousand that were produced were used by the peace-time military for many years and were also used extensively for the mail service. Charles Lindburg hauled mail in them before his Atlantic flight. Equally famous was the DH-4 power plant, the 400-horsepower V-12 Liberty engine.