He spent all his savings and then borrowed more to go to England at his own expense and join the Royal Flying Corps.
He enlisted in England early in 1916 as an Air Mechanic, but his brilliance received immediate recognition, and after three weeks he was gazetted Second Lieutenant, and by July 1916, Harry Butler was flying in France.
His second greatest talent proved to be as an instructor. Flying daily, and teaching others the thrill and achievement that man could find in the air, this must have been a very happy period in his life. Living with airminded men, he shared with them his knowledge and uncanny instinct for aviation. Other men could be taught to fly, but Harry Butler was always an airman born.
He was soon made Captain and Flight Commander, and during his service as an instructor 2,700 pupils passed through the school to which he was attached. This in itself was a magnificent contribution to the Allied war effort, but Harry Butler adopted a typical instructor’s routine of his own that added further merit to his service.