The paper highlights the investigation into the peculiarities of transforming the psychophysiological functions of the flight personnel. It also deals with the assessment of the level of the emotional tension and tiredness which develop in the process of the participation in the peacekeeping mission on the territory of the African continent. The investigation has been carried out by means of the software and hardware system ПФИ-2 Chronoreflexometer». The helicopter unit flight personnel has been examined before its participation in the peacekeeping mission and after its nine-month-long stay in the Republic of Liberia. It has been established that the nine-month-long participation in the peacekeeping mission resulted in the development of tiredness in the flight personnel, the above being proved by the worsening of the following parameters: simple visual-motor reaction -by 133%, variability of simple visual-motor reaction – by 210%, premature reaction to the moving object-by 160%, the number of the premature reactions to the moving object – by 192%, the number of retentions in the reaction to the moving object – by 493%, the duration of regular reactions in time of assessing the spatial orientation – by 179%, the number of error reactions under assessing spatial orientations – by 202%, the number of error reactions under assessing spatial orientation – by 211%. A number of parameters remained constant: the latent period and variability of the complex visual-motor reaction, the functional movability of nervous processes, the duration of retarded reactions to the moving object. It has been shown that the psychophysiological functions whose level has not changed considerably (but in some cases has even improved) can be used for assessing the professional suitability during the professional selection and monitoring of professionally important qualities of the flight personnel.