A Zeppelin is a type of rigid airship (or dirigible) pioneered by Count Ferdinand von Zeppelin in the early 20th century based in part on an earlier design by David Schwarz. Due to the outstanding success of the Zeppelin design, the term zeppelin in casual use came to refer to all rigid airships. These giant aircraft were used for passenger transport as well as for military purposes. The DELAG (Deutsche Luftschiffahrts-AG), which can be considered the first commercial airline, served scheduled flights well before World War I, and after the outbreak of the conflict, the German military made extensive use of Zeppelins as bombers and scouts.