Correlation plots for the eleven planets studied in this paper. Detections are shown as blue points and upper limits as orange points. We pinpointed with a gray area the parameter space that seems to favor the detection of metastable helium in exoplanet atmospheres. Top left: δR_p/H as a function of the stellar mass. Top right: δR_p/H as a function of XUV flux received from 5 to 504 A. Bottom left: mass-loss rate derived from the p–winds simulations as a function of the stellar mass. Bottom right: mass-loss rate derived from the p–winds simulations as a function of XUV flux received from 5 to 504 Å.