Although the Liberty engine became a potent factor in World War I, its greatest achievements were to come in the years following, when for the first time aviation’s horizon was lifted above the level of county-fair stunt exhibitions and the foundation laid for commercial aviation. It was the Liberty engine that first enabled man to conquer the ocean in an airplane. Four of the 440-horsepower engines powered the famous U. S. Navy NC-4, which in 1919 became the first plane to fly the Atlantic. [Illustration: Aerial mastery of the Atlantic was first achieved in 1919 in the Liberty-powered NC-4, shown in this U. S. Navy photograph.] [Illustration: The Martin MB-2 was used by General Mitchell in the 1921 tests which indicated the destructive ability of big bombing planes. Liberty engines supplied the power.] Two years later, when General “Billy” Mitchell conducted his historic and dramatic demonstration of the potency of air power, Liberty-powered planes were called upon to do the job. The big bombers, as Mitchell had predicted, sank a 22,000-ton German battleship in only twenty-five minutes. In April, 1923, the Liberty was again in the headlines. Two Army pilots, Lieutenants Oakley Kelly and John Macready, flying a Fokker airplane powered with a Liberty engine, stayed aloft for thirty-six consecutive hours, shattering all previous endurance marks. Later the same year they completed the first non-stop transcontinental flight, again using the Liberty-powered Fokker. The following year still another achievement was added to the Liberty’s long series of successes. Two Douglas Cruisers, powered with Liberty engines and prepared for the flight at Dayton’s old McCook Field, became the first planes to circle the globe, covering 26,345 miles in 363 hours of actual flying time. [Illustration: The famous De Haviland 4, British-designed observation plane of World War I. The ship shown here is an American version, built by the Dayton Wright Airplane Company in 1918 and powered with a Liberty engine. At left is Orville Wright, consultant for the company, shown with Howard Rinehart, a test pilot.] [Illustration: The first planes to complete a trip around the world were two Douglas Cruisers, one of which is shown above. There again, the Liberty engine helped establish a memorable record in aviation history.] Besides holding at one time the world’s speed and altitude records, the Liberty also was the engine that first made the concept of air-mail service more than just a dream. Charles A. Lindbergh was among the pioneer pilots of the early 1920’s who flew Liberty-powered De Haviland mail planes along relatively uncharted air lanes through all types of weather.