Today in Aviation History 9 October 1906 – (DEU) Zeppelin LZ 3 flies for the first time. A Zeppelin is a type of rigid airship named after the German Count Ferdinand von Zeppelin (German pronunciation: [ˈt͡sɛpəliːn]) who pioneered rigid airship development at the beginning of the 20th century. Zeppelin’s notions were first formulated in 1874 and developed in detail in 1893. They were patented in Germany in 1895 and in the United States in 1899. After the outstanding success of the Zeppelin design, the word zeppelin came to be commonly used to refer to all rigid airships. The principal feature of Zeppelin’s design was a fabric-covered rigid metal framework made up from transverse rings and longitudinal girders containing a number of individual gasbags. The advantage of this design was that the aircraft could be much larger than non-rigid airships, which relied on a slight overpressure within the single pressure envelope to maintain their shape. The framework of most Zeppelins was made of duralumin (a combination of aluminum and copper as well as two or three other metals—its exact content was kept a secret for years). Early Zeppelins used rubberised cotton for the gasbags, but most later craft used goldbeater’s skin, made from the intestines of cattle. LZ 3 became the first truly successful Zeppelin. This renewed the interest of the German military, but a condition of purchase of an airship was a 24-hour endurance trial. This was beyond the capabilities of LZ 3, leading Zeppelin to construct his fourth design, the LZ 4. Before World War I (1914–1918) the Zeppelin company manufactured 21 more airships. The Imperial German Army bought LZ 3 and LZ 5 (a sister-ship to LZ 4 which was completed in May 1909) and designated them Z 1 and Z II respectively. Z I flew until 1913, when it was decommissioned and replaced by LZ 15, designated ersatz Z I.