Another proponent of the sabotage hypothesis was Max Pruss, captain of the "Hindenburg" throughout the airship's career. Pruss flew on nearly every flight of the "Graf Zeppelin" since 1928 until the "Hindenburg" was launched in 1936. In a 1960 interview conducted by Kenneth Leish for Columbia University's Oral History Research Office, Pruss said early dirigible travel was safe, and therefore he strongly believed that sabotage was to blame. He stated that on trips to South America, which was a popular destination for German tourists, both airships passed through thunderstorms and were struck by lightning but remained unharmed.