Curtiss became an actual father has well. In 1912, his wife gave birth to a second child, Glenn Curtiss, Jr. Anticipating the responsibilities of fatherhood, Curtiss already had given up exhibition flying.
A year later, he visited the airplane factory of Thomas Sopwith in England, who was building tractor airplanes. Unlike the earliest airplanes, with propellers in the back that pushed planes forward, tractor aircraft have propellers up front, like most contemporary aircraft. Sopwith’s designs, plus the U.S. Army’s interest in tractor training aircraft, put Curtiss into high gear as an airplane builder. His first major tractor airplanes were the JN-1 and JN-2. He followed those models with the JN-3, of which he built fewer than 100. In 1916, Curtiss modified the JN-3 to improve its performance and named the new model the JN-4, nicknamed the Jenny. Over the next few years, he came out with over fifteen versions of this plane and manufactured more aircraft than any other American during World War I.
In 1914, Curtiss once again incurred the ire of the Wright family. In an attempt to prove that Samuel P. Langley had invented the first machine capable of sustained flight, the Smithsonian Institution contracted with Curtiss to verify if Langley’s 1903 Aerodrome could fly. The Smithsonian shipped Langley’s machine to Hammondsport, where Curtiss and his associates modified it and eventually flew it off of Lake Keuka on May 28 and June 2. The Smithsonian’s witness for these flights, Dr. Albert Zahm, later concluded that the Aerodrome “has demonstrated that with its original structure and power, it is capable of flying with a pilot and several hundred pounds of useful load. It is the first aeroplane in the history of the world of which this can truthfully be said.”