When the United States entered World War I on 6 April 1917, the Air Service of the United States Army existed only as a branch of the Signal Corps, and was known by the name of Aviation Section, U.S. Signal Corps. It consisted of 1,120 personnel, of which 65 were officers. The Army was not ready for the deployment of aviation forces to Europe, and it became necessary to prepare after President Woodrow Wilson's declaration of war.
As part of the buildup of US forces, aviation units were formed into aero squadrons primarily at Kelly Field, San Antonio, Texas, with additional units being formed at Rockwell Field, San Diego, California. Once formed, and prior to their deployment to Europe, Camp Taliaferro, north of Fort Worth, Texas, and several airfields near Toronto, Ontario, Canada were used by the British Royal Flying Corps (RFC) to perform flight training for the new aero squadrons. Camp Hancock, near Augusta, Georgia, was used for training service squadrons of aircraft mechanics as well as flight training.
When ordered to deploy, units departed though Garden City, New York, which was the primary port of embankment. Units there were loaded onto transport ships for the trans-Atlantic crossing. Upon arrival in Europe, Liverpool, England, and Brest, France, were the primary ports of disembarkation, although other ports were also used. Some aero squadrons arriving in England received additional training from the Royal Flying Corps, and later the Royal Air Force (RAF) once it was established, and were then attached to British squadrons, deploying with them to France. Others received further training and were sent to Winchester, Hampshire, where they awaited their cross-channel transfer to France, using the port of Southampton.