The investigation into the accident concluded that static electricity had ignited hydrogen which had leaked from the gasbags, although there were allegations of sabotage. 13 passengers and 22 crew, including Ernst Lehmann, were killed. Despite the apparent danger, there remained a list of 400 people who still wanted to fly as Zeppelin passengers and had paid for the trip. Their money was refunded in 1940. Graf Zeppelin was retired one month after the Hindenburg wreck and turned into a museum. The intended new flagship Zeppelin was completed in 1938 and, inflated with hydrogen, made some test flights (the first on 14 September), but never carried passengers. Another project, LZ 131, designed to be even larger than Hindenburg and Graf Zeppelin II, never progressed beyond the production of a few ring frames. Graf Zeppelin II was assigned to the Luftwaffe and made about 30 test flights prior to the beginning of World War II. Most of those flights were carried out near the Polish border, first in the Sudeten mountains region of Silesia, then in the Baltic Sea region. During one such flight LZ 130 crossed the Polish border near the Hel Peninsula, where it was intercepted by a Polish Lublin R-XIII aircraft from Puck naval airbase and forced to leave Polish airspace. During this time, LZ 130 was used for electronic scouting missions, and was equipped with various measuring equipment. In August 1939, it made a flight near the coastline of Great Britain in an attempt to determine whether the 100 metre towers erected from Portsmouth to Scapa Flow were used for aircraft radio location. Photography, radio wave interception, magnetic and radio frequency analysis were unable to detect operational British Chain Home radar due to searching in the wrong frequency range. The frequencies searched were too high, an assumption based on the Germans' own radar systems. The mistaken conclusion was that the British towers were not connected with radar operations, but were for naval radio communications. After the beginning of the Second World War on 1 September, the Luftwaffe ordered LZ 127 and LZ 130 moved to a large Zeppelin hangar in Frankfurt, where the skeleton of LZ 131 was also located. In March 1940 Göring ordered the scrapping of the remaining airships, and on 6 May the Frankfurt hangars were demolished. Cultural influences Zeppelins have been an inspiration to music, cinematography and literature. The 1930 movie Hell's Angels, directed