During the crosing of the Sahara, Nott made the flight shown immediately below, left.  It was one of a series of five Nott made showing that "cold descent" from high altitude was safe. Cold descent occurs when the burner is off and the balloon acts as a parachute for a long period of descent. At the time of these flights nothing was known about their safety and these experemintal flights were a bold step into the unknown.  However making a cold descent subsequently became standard training that every pilot must complete before he can receive his balloon licence.