In the late 1930s, most of the Aeroflot fleet consisted of small biplanes like this Polikarpov R-5, reveals Vandermueren. He writes: 'The route from Stalinabad (now Dushanbe), the capital of the Tajik SSR [Soviet Socialist Republic], over the Pamir mountains to Khorog (pictured here in 1937) is still considered one of the world’s most dangerous air routes'