Question: What type of aircraft did the Italian engineer Enrico Forlanini work on that was an aerostat?

full_context: Document 1: Cloud Nine (tensegrity sphere): Cloud Nine is the name Buckminster Fuller gave to his proposed airborne habitats created from giant geodesic spheres, which might be made to levitate by slightly heating the air inside above the ambient temperature.
Document 2: Umberto Nobile: Umberto Nobile (] ; 21 January 1885 – 30 July 1978) was an Italian aviator, aeronautical engineer and Arctic explorer. Nobile was a developer and promoter of semi-rigid airships during the period between the two World Wars. He is primarily remembered for designing and piloting the airship "Norge", which may have been the first aircraft to reach the North Pole, and which was indisputably the first to fly across the polar ice cap from Europe to America. Nobile also designed and flew the "Italia," a second polar airship; this second expedition ended in a deadly crash and provoked an international rescue effort.
Document 3: Airship: An airship or dirigible balloon is a type of aerostat or lighter-than-air aircraft that can navigate through the air under its own power. Aerostats gain their lift from large gas bags filled with a lifting gas that is less dense than the surrounding air.
Document 4: Giuseppe Mario Bellanca: Giuseppe Mario Bellanca (March 19, 1886 – December 26, 1960) was an Italian-American airplane designer and builder who created the first enclosed-cabin monoplane in the United States in 1922. This aircraft is now on display at the National Air and Space Museum's Steven F. Udvar-Hazy Center.
Document 5: Metal-clad airship: Metal-clad airships are airships which have a very thin airtight metal envelope, rather than the usual fabric envelope. This shell may be either internally braced as with the designs of David Schwarz, or monocoque as in the ZMC-2. Only four ships of this type are known to have been built, and only two actually flew: Schwarz's aluminum ship of 1893 collapsed on inflation; Schwarz's second airship flew at Tempelhof, Berlin in 1897, landed but then collapsed; the ZMC-2 flew 752 flights between 1929 and scrapping in 1941; while the Slate "City of Glendale", was built in 1929 but never flew.
Document 6: Enrico Mosconi: Enrico Mosconi (1843-1910) was an Italian engineer, father of the General Enrique Mosconi. He had active participation in construction of the railways in the Argentine Republic.
Document 7: Solar balloon: A solar balloon is a balloon that gains buoyancy when the air inside is heated by solar radiation, usually with the help of black or dark balloon material. The heated air inside the solar balloon expands and has lower density than the surrounding air. As such, a solar balloon is similar to a hot air balloon. Usage of solar balloons is predominantly in the toy market, although it has been proposed that they be used in the investigation of planet Mars, and some solar balloons are large enough for human flight. A vent at the top can be opened to release hot air for descent and deflation.
Document 8: Enrico Bernardi: Enrico Zeno Bernardi (Verona, 20 May 1841 – Turin, 21 February 1919) was an Italian engineer and one of the Italian automobile pioneers. As a child growing up in Verona, Bernardi spent much of his free time in blacksmiths' workshops learning the skills to put his inventive abilities into practice. In 1856, he entered a mechanical model of a steam engine and locomotive in the Verona Agricultural Exhibition, where he earned an honorable mention for his work.
Document 9: List of Forlanini airships: This is a complete list of Forlanini airships designed and built by the Italian pioneer Enrico Forlanini from 1900 to 1931 (posthumously). These, like the German Groß-Basenach semi-rigid airships, were the first to have the gondola attached to the envelope, to reduce air resistance.
Document 10: M-class blimp: The Goodyear Aircraft Company of Akron, Ohio built the M-class blimp for the US Navy as the follow-on to the K-class anti-submarine warfare blimp used during World War II. It was a significantly larger airship. Four airships, designated M-1 through M-4, were delivered in early 1944. Operations of K-ships in tropical regions had shown a need for a blimp with greater volume to offset the loss of lift due to high ambient temperatures.
Document 11: Carlo Forlanini: Carlo Forlanini (11 June 1847 – 26 May 1918) was an Italian physician. He was the elder brother of aviation pioneer Enrico Forlanini.
Document 12: Viale Enrico Forlanini: The Viale Enrico Forlanini is a long street located in Milan, Lombardy, Italy. It cuts through a park, connecting the city centre with the Linate Airport and the Idroscalo lake. The street is named after Milan-born aviation pioneer Enrico Forlanini (1848–1930). However, it was originally named after Michele Bianchi (1883–1930) of the National Fascist Party.
Document 13: Inflatable air cushion: An inflatable air cushion is a bag of fabric or plastic that can be inflated to provide cushioning. Unlike Bubble Wrap, inflatable air cushions have a check valve to allow the cushion to be inflated or sometimes deflated.
Document 14: Enrico Forlanini: Enrico Forlanini (13 December 1848 – 9 October 1930) was an Italian engineer, inventor and aeronautical pioneer, known for his works on helicopters, aircraft, hydrofoils and dirigibles. He was born in Milan. His older brother Carlo Forlanini was a physician.
Document 15: Hopper balloon: A hopper balloon (simply hopper) is a small, one-person hot air balloon. Unlike a conventional hot air balloon where people ride inside a basket, there is no basket on a hopper balloon. Instead, the hopper pilot usually sits on a seat or wears a harness similar to a parachute harness. Hoppers are typically flown for recreation. These aircraft are sometimes called "Cloud Hoppers" or "Cloudhoppers." However, these terms formally refer to the products of a particular manufacturer, specifically Lindstrand Balloons. Nonetheless, "Cloudhopper" is used by many people as a genericized trademark, which refers to all craft of this general type. Most hopper balloons have envelopes that range in volume from 14000 to and have a maximum flight duration of 1 to 1.5 hours. The two principal commercial balloon manufacturers today offering hopper balloons for sale are Cameron Balloons and Lindstrand Balloons. Most other hopper balloons are experimental aircraft designed and built by amateur constructors.
ground_truth: airship