The article analyses air transport system and presents reasons of air incidents and flight safety estimation score. Dependence of air accidents amount per 100 000 flight hours is compared to typical time dependent behavior of failure rate and divided into three intervals. The intervals are analyzed and the reasons of change of parameter score are submitted. Statistical characteristics of the number of accidents per interval parameter are provided. Parameter of air accidents per year matches the Weibull distribution; estimations of Weibull distribution parameters are submitted. Probability of accidents is calculated for each interval; obtained results are analyzed. Ways for furthering flight safety and air transport system are suggested.