Since the beginning of hostilities in Vietnam, a real helicopter war took place over the jungle. Combat helicopters performed tasks of landing, reconnaissance, cargo transportation and fire support. Many operations during the Vietnam War were characterized by the combined use of transport and attack helicopters. The intensity of flights was very high, especially for the crews of fire support helicopters. Difficult climatic conditions, typical for the jungle zone, together with the peculiarities of work in closed cockpits made the combat service of helicopter crews extremely difficult. The result of such high stress was pilots’ fatigue, which, in turn, could affect the results of combat missions. This is evident from the high combat losses – over eleven years of military operations in Southeast Asia, 2190 helicopter pilots were killed. At the same time, helicopters were a formidable weapon that brought great benefits to the ground units of the U.S. Army and Marines.