Longitudinal retrospective study has revealed the changes in the health of 706 pilots and air navigators and in the hemoglobin (Hb) and erythrocyte levels in peripheral blood once within a 5 year period. The duration of an examination is 10 years and even longer. It is established that the Hb concentration increased with an increase of the age. At the age of 20-30, this parameter is lower in persons being healthy for a long time. An analysis based on curve plotting of the remainder of life time indicated that the high level of Hb and high mean concentration of Hb in the erythrocytes have an adverse effect on the health and flight fitness. The regularities are noted within the normal values and validate a differentiated approach to evaluating the results of diagnostic examinations instead simplified normal-non-normal estimates.