The First World War was the introduction of Aircraft that was used on a large scale but Observation Balloons had been in use for several years before hand, generally the Balloons were used for Artillery spotting. The British relied on the French regarding their knowledge in the Aircraft industry during the early years of the First World War although the Americans became totally dependant on the French and British Aircraft suppliers when the Americans joined in the War late in 1917. The very early Aircraft were limited in carrying small bombs and Bomb sights were in very early development but early bombing missions started as early as September 1914 with the bombing of the German Airship sheds in D├╝sseldorf, Cologne and Friedrichhafen.