Para cross-country skiing is an endurance sport for athletes with visual and physical impairments, who are classified into three categories and further divided into sport classes based on the severity of their impairment. The number of participants is limited, therefore athletes in different sport classes within the same category compete together, potentially compromising race fairness. A time factor system is applied to address this issue: it consists of a percentage factor associated with each sport class to correct the athlete’s finishing time. The thesis focused on a specific type of competition using a mass start procedure, where participants in the same sport class start simultaneously.