Transmission spectrum of HD 189733b (top panel) and WASP-69b (bottom panel) atmospheres in the region of the Na I D doublet. The atmospheric transmission spectrum is presented in light gray. We show the binned transmission spectrum with black dots; 20 pixels (top) and 10 pixels (middle). The Gaussian fit to each Na I D line is shown in red with its residuals in the bottom. The expected wavelength position of the Na I doublet lines, in the planetary reference frame, are indicated with blue vertical lines and the red horizontal line is used as reference around zero. A net blueshift of ~ 3 km s^-1 (~ 0.04 Å) is observed in the Na I lines of HD 189733b, possibly due to a global error on the planetary RV shift as a result of the HARPS precision. No shift is observed for WASP-69b Na I lines with respect to the reference wavelength frame. The uncertainties of the relative flux are assumed to come from photon and readout noise propagated from the original spectra.