[Evaluation of the impact of an increased flight duty period on flight safety]

Scientific rationale has been provided for the qualitative indices of the time of flight from the studies of the impact of a gradual (by small values) increase in the time of flight on its safety and the health of airmen. Analysis of the 2003-2004 flight safety trends, by studying the specific changes in a flight crew's working load from the pilot performance quality index and airmen's health status revealed no negative impact of an annual working load increase on the incidence of diseases leading to pilots' medical disqualification. Flight safety indices did not become worse when the flight timeout was increased up to 90 hours during 30 successive hours and 900 hours during a year. Increasing the load of 90 and particularly 100 hours during 30 successive days may present a potential threat to flight safety.