Ed Yost own interests turned toward reviving the lost practice of manned hot-air ballooning. This technology had first been invented in France by in the late 18th century by pioneers led by the Montgolfier brothers, but under the Montgolfier system, the balloon's air was heated by a ground fire prior to the balloon being released. The inherent danger of this type of balloon flight led to the system being abandoned when hydrogen and later helium became available. One of Yost's key engineering insights was that a hot-air balloon could be made to carry its own fuel. The invention of relatively light burners
Organization of the Air Service of the American Expeditionary Force "observation wings" were created to coordinate the reconnaissance activities of the five corps air services. The basic units of the air service were the squadron for powered aircraft and the company for balloons. 45 squadrons (38 of which conducted combat operations) of aircraft and 17 companies of balloons served at the front. The 20 pursuit and seven bombardment squadrons were authorized 25 aircraft (including spares) and 18 crews each by the "Field Service Regulations", while the 18 observation squadrons were each authorized 24 planes and 18 crews. Balloon companies were equipped with one balloon and approximately six observers each. The