The article presents the results of the earth structures’ bearing capacity evaluation and objectification for airfields by means of CBR (California Bearing Ratio) parameter. In order to quantify actual terrain conditions, in situ testing methods are advancing against laboratory testing. However, the optimal solution is to combine precise laboratory testing with in situ measurements. A correlation between CBR values and moisture content values of the backfilling soil of runway strips from earth structure of Žilina Airport was made within the frame of author's research activities. The CBR tests were performed on the clayey gravel specimens, which were prepared in the test cylinders used for a Proctor modified test. It has been found that the correlation allows determining of the moisture level to meet requirements of the RWY recommended by Aerodrome Design Manual [1]. The newest results of CBR in situ measurements on the aerodrome earth structures are also presented. CBR in situ values were objectified by the CLEGG device WS 32830. This device quantifies the value of rate of compaction from in situ tests based on CIV values (Clegg Impact Value) [2].