Seasonal behavior of vertical distribution of the ozone concentration within the layer from 0 to 7000 m is analyzed by the data of aircraft measurements for the period 1998-2000. It is shown that tropospheric ozone is mainly formed in situ inside the inner mixing layer in the spring period. Variation of the ozone concentration at different heights is sufficiently synchronous, that is indicative of weak income of ozone from the stratosphere. Data on the absolute maxima of ozone concentrations at all heights inside the layer under study are presented.