In the early 1960s, the DuPont company (USA) patented a method for producing what was called a fasciated yarn, which is composed of a core of more or less parallel fibres, wrapped around by a small proportion of surface fibres. A false twist air jet was used as the twister, hence the name air jet spinning or air vortex spinning. Air-jet spinning is the most promising spinning method at the beginning of the twenty-first century. It offers the fastest means of industrial production of staple fiber yarns. The main feature that distinguishes the morphology of air-jet spinning from the other