since the Aereon in 1863, and numerous inventors were working on airship and aircraft designs (the idea that a secretive inventor might have developed a viable craft with advanced capabilities was the focus of Jules Verne's 1886 novel Robur the Conqueror). In fact, two French Army officers and engineers, Arthur Krebs and Charles Renard, had successfully flown in an electric-powered airship called La France as early as 1884, making no fewer than seven successful flights in the craft over an eleven-month period. Also during the 1896–97 period, David Schwarz built an aluminum-skinned airship in Germany that successfully flew over Tempelhof Field before being irreparably damaged during a hard landing. Both events clearly demonstrated that the technology to build a practical airship existed during the period in question, though if reports of the capabilities of the California and Midwest airship sighted in 1896–97 are true, it would have been considerably more advanced than any airship built up to that time. Several individuals, including Lyman Gilmore and Charles Dellschau, were later identified as possible candidates for being involved in the design and construction of the airships, although little evidence was found in support of these ideas. Claims of extraterrestrial origin Early sources citing the extraterrestrial hypothesis, all from 1897, include the Washington Times, which speculated that the airships were "a reconnoitering party from Mars"; and the Saint Louis Post-Dispatch, which suggested of the airships, "these may be visitors from Mars, fearful, at the last, of invading the planet they have been seeking." In 1909, a letter printed in the Otago Daily Times (New Zealand) suggested that the mystery airship sightings then being reported in that country were due to Martian "atomic-powered spaceships." See also Airship Ghost rockets Footnotes References . . . . . . . . . , 213 pp. . . Unidentified flying objects Airships 1890s in the United States