Fig. 3. Analysis of variations in flight direction relative to the wind direction (H-W) for three selected trackings (same tracks as in Fig. 1). The first column presents the deviations from a perfect headwind orientation over the entire tracking. In the second column, there are autocorrelation diagrams for tracks A and B. The last column is an alternative analysis of periodicity, in the form of a DFT power spectrum, showing the relative frequency content of the H-W data series. Track A has an autocorrelation period of approximately 160s and a significant frequency component of 6.74 mHz. Track B shows no distinct period, and the frequency peaks fail to pass the significance level.